Could it be the interlock fabric stretched while you were working w/it?

Rather difficult to guess what's going on w/ so little info
= S

& no offense, but might it be you & not the pattern?For instance, I know I used to gain as much as an inch or more in various places @ certain times of the month.....

That said, mistakes are how we learn - I can't even count the number of 'failed' &/or abandoned sewing projects I've had ; J

There is different fit with different fabrics with knits being the worst offender...they stretch more horizontal than vertical. You are choosing knits for your pattern, you have to read on the pattern envelope how much stretch is allowed as all knits are not created equal.

The same goes with wovens...depending on the fabric, you will get a different fit...thicker fabrics, you allow for bulk in the fit.

Don't feel bad, you aren't confused, it's one of those things that happens to everyone.

Yes, please keep on trying. Knits are so comfortable and once you get the hang of sewing them are great wardrobe buuilders. Generally speaking, patterns designed for knits won't work in wovens. Make sure that you are using the stretch across the body and not for the length of the garment. Cotten interlock can be tricky to sew and easily stretches out of shape. Lycra blends are a little more forgiving. I don't know why your lycra garment was too wide and too short (at least I think that's what you are saying)

A pattern company that is great for learning to sew knits is Kwik Sew. Pick your size based on your high bust measurment (just under the arms) and use the knit guide printed on the pattern envelope to make sure you have the required stretch in your fabric. Good Luck