I am on the depo birth control and I was wondering if it was safe to let my partner ejaculate inside of me. I worry constantly about everything and for once I want to not worry

There is always a risk,

If you worry that much, maybe you need to abstain. All birth control has risks. Have your partner use a condom or use spermicidal foam too.

I moved your question from Teens in Relationships to Child & Teen Health a medical board since this is not a relationship question.

How old are you?

Birth control/contraceptives can only reduce the chance of pregnancy. Refraining from sex is the only way to fully prevent pregnancy.

If you aren't ready to entertain the thought of being a parent or making the other very adult choices that come with sex, tell your boyfriend 'no'. He won't be the one making the final decisions if you do become pregnant.

Have your partner use a condom as well. There is always a risk

Most women on depo use just that as the form of birth control that they rely on. Obviously you need to be certain to have your injections on time. To lessen the chance of pregnancy even more, have your partner always use a condom, and make sure it is also used correctly. To completely eliminate the chance of pregnancy you would have to stop having sex.

No form of birth control is 100 percent, and you said "inside" if you are having sex and he is "pulling out" that is a risk, since there is sperm in the early fluids, so even that has a risk.

Also it (depo) provides ZERO protection against HPV that is epidemic among people your age. Which can cause cervical cancer...

Not to mention every other SD out there.