Please post a picture of the entire plant.

Beyond that, is it in the ground or a container?
And why are you spraying regularly? That's seldom needed if the plants are healthy.
And tell us more about how & when you water and/or fertilize.

it is in a container. I said I spray regularly because I had flies that came regularly to invade the plant.I have tomato dust, Yates prytherum spray and a Eco oil botanic oil that is to be diluted with water. I dont use them all at once only when i see flies

I live in Adelaide. Its just started Spring here and for the last week it was raining and extremely windy like crazy and thats also the reason why the stem got blown off and broken. but the wheather is now sunny and warm like spring. I checked the humidity yesterday I think its been around 80-90% these days.

I have been growing this plant for almost 1 and a half years now. I didnt know how to care and in first half year of planting it almost died on me because i didnt drain out water and didnt feed much fertiliser and the soil was always wet almost drowned it. I did have fly pests problems before but its now getting better (only a few will come around, so i dont think this condition is caused by the flies). For the past half year its been healthy and green but now is getting sick.
I did some research and now I keep it well drained by putting a pot feet, regular tomato fertiliser (to increase nitrogen as I didnt feed much anything before). seaweed solution just added yesterday. I fertilise every 10-14 days. I water when the soil down 5 cm is dry to touch. Water til water comes out of drainage hole.

For the stem, I guess I have to cut it off, the leaves now looking very curly. Can I use it to clone another plant??? My current plant stem is not straight i guess the seeds were crowded and no space when i first put them..
Thank you for reading this long reply. I just cant figure out what is the disease causing this problem.
Susan

Here is a link that might be useful:

The plant doesn't look too bad. A little leggy maybe. How much sun is it getting? I would remove the red stuff on top of the pot, it's not helping. Try and give it more sun if possible.

But i thought applying a red plastic mulch would help soil from getting dried out because of the sun??

yes, it was all windy and rainy before and now just started spring. These two days are sunny.
Do you guys know what kind of problem this plant is having?

Your plant is not sick, it's just not growing! After 1 1/2 years of continual growth, under decent conditions it should be about the size of a small house. I'm amazed it has lived so long and still looks basically healthy. What size is the pot? I'm assuming it has drain holes. What kind of soil is in the container? How much sun per day it it getting? How often do you water? How do you know that it needs watering. If you had a good draining container mix, and decent sun light, and average fertilizer, you should be able to grow a plant that size in a month, not 1.5 years. If you are serious about growing in a container check out the Container Gardening forum on this site for a good container mix to use.

so if its not sick, how come its got all those yellowing leaves??
i will reply all questions in next message. gotta think in my head now ;)

Its very strange. Some people say my plant has a bacteria problem, some say its a virus and you say its not sick...someone even told me to trash it...sigh..how can i just trash it after growing for 1.5 years, i am just a avergage gardener..not a farmer..

The pot is a clay pot, average size, fat wide but not as tall as a average bucket, with a drain hole.

The soil is potting mix

It was winter here so its just sort of getting full sun shine these days

I used to drown the plant in the first year but dont do it anymore. only water when dry to touch 5cm down.

I use tomato fertiliser with rich nitrogen source and other minerals like potassium. I also watered with seaweed solution last weekend.

The broken stem is still in place and it looks like flowers are opening and fruits are getting bigger.

If you say it can be grown in a month..i will wait more time and see..if its still the same, i will put in the bin

You must also be talking to someone else, because no one on this thread said it was sick with a virus or bacteria, and that you should pull it. If it's been alive for 1.5 years as you say, leaves don't live forever and some yellowing, even dying can be expected. I say it's not sick because yes, you pulled a few yellowing leaves, but the plant I see in the picture has leaves that look good, and if it's been alive for a year and a half you must be doing something right. I'm just wondering how come it didn't grow all last year if it's getting full sun. Are you using potting mix or potting soil? I asked about pot size, because it's kind of hard to tell by the picture. I'm assuming that it looks about 5 gallons which should be big enough. All I can think of is that you might have used potting soil and have some perched water in the pot which might be stunting the growth. I use a skewer to tell if my containers need water. I insert the skewer about 12" down and remove it to see if the bottom of the pot is wet or dry. You also might considering posting this on the "container" forum and see what answers you get. Other than that all I can suggest is waiting and see if the fruit develops. What kind of tomato plant is it? Where is Adelaide? Must be in Southern Hemisphere somewhere.

It depends what you want out of this tomato plant. If you are expecting a good crop then that isn't going to happen after all this time. If you are doing it for fun then it doesn't look too bad to me. I always cover the pot with comfrey (not sure if you can get that in Australia. It grows wild in England and breaks down giving nutrients to the tomato and keeps it from drying out. Redo again in a month.
If you desperately want to grow this variety again then wait until the tomato is ripe and collect some of the seed from it and try again next year.