What have you been doing to it, and where have you been keeping it?

I have had it since 2/20/17 It came with buds and bloomed for me. I was keeping it in a window that gets some Northeast sun... then someone told me that I should treat it like a normal tree and keep it outside in a protected area. I did that and it seemed to do fine... its only lately that its looked sickly...I have never pruned it till now...I pruned off the dead branches. I have only watered and did not know what to feed it.

Well, it is a deciduous tree and it's getting on to be that time of year. When you pruned off the dead branches, what color was the cambium?

Where they naturally occur, or in the landscape, Syringa demands good drainage and doesn't tolerate wet feet well. Your soil is very water retentive, and this is a significant problem because it makes it very difficult to water w/o over-watering in the shallow pots we use. Your focus should be on maintaining its viability until it can be repotted in spring. Too, I'm not sure your plant will experience enough chilling in SF, even outdoors, to satisfy its dormancy needs. Are there lilac trees in the landscape where you live?

Your tree wants to be outdoors, permanently. You should monitor it's moisture needs with a piece of 1/4" wood dowel rod that's been sharpened in a pencil sharpener, or a bamboo skewer - only water when it actually needs watering, and you should water to well beyond the saturation point, so at least 15-20% of the water used to wet the soil exits the drain hole. After you water, hold the pot over the sink and move it up and down. You'll discover that on the reversal from downward to upward, excess water will exit the pot. This is very important. Hopefully, this strategy will help you keep the plant viable until spring, when you can repot into an appropriate soil.

It needs regular fertilizing as well. Typically, Syringa wants a low N fertilizer in order to bloom. Your focus shouldn't be on blooming at this point - it should be on getting the tree healthy and development. For now, Foliage-Pro 9-3-6 would be an excellent fertilizer, and can be used on virtually all the plants you grow. I use it for more than 75 species of bonsai, and all my 'other' plants. I only do a little tweaking for a few plants - tomato, hibiscus, boxwood.

Let me muse, please: No one is a 'natural' when it comes to bonsai. Some, unlike me, are blessed with exceptional artistic vision; and some, as a byproduct of their profession, already have a sound understanding of plant physiology - how plants work. The rest of us, if we're to become proficient to the point that we can consistently keep our trees healthy, will have to either invest the time it takes to form a good understanding of soil science and plant physiology, or, be content to continue buying plants to replace those that are no longer viable. The later gets to be frustrating very quickly, and is the reason more than 95% of those who try their hand at bonsai don't pursue it beyond a year or two.

Wishing you the very best luck. If there are questions you think I might be able to answer, don't hesitate to ask. Your battle, re your tree, is against poor root health.

Al