I use to have a regular period until I started taking the birth control shot. I only got it once and stopped cause I bled for 3 or 4 months so I switched to the pill and my cycly became regular. I stopped taking it and now I have a period every 14 days is this bad . How do I know when I'm ovulating?

This is probably because your homones are doing back flips from being on the shot, then stopping it, then being on the pill, and stopping it...
You need to get your body in a routine, starting and stopping different hormonal medications like the pill and the shot messes up your period.
And for ovulating, that's hard to say since your cycle is so messed up.

The Depo Provera injection you received often causes abnormal vaginal bleeding. Then switching to the pill sorted you out. Now, hormonally speaking, you are on your own and it may take a few months for things to reregulate. As to bleeding every two weeks, no it isn't bad in the short run, but if it persists then it must be addressed. Some other things to consider would be how long are you bleeding for, how heavy, etc. This can lead to anemia, there may be a thyroid issue, etc. And you are "probably" not ovulating but you can't be absolutely sure. If sexually active you need contraception unless you want a pregnancy.