I Need Advice!

So I have been sexually active with this guy since November and I have strong feelings for him. We have talked about a relationship at the beginning but it kind of just drifted into just a sex relationship. Over the months we have had unprotected sex where he has came inside me a few times. We both agreed that we didn't want a kid so soon so I took a plan b pill one time and I didn't like the fact that it changed my cycle. Meaning I didn't have a period for a month and my period went from the from the beginning of the month to the end of the month. Now I told him that it scared me to where I don't want to take it again. So the other time where he came inside me we just waited it out to see if I was pregnant or not. Luckily I didn't get pregnant. Just two weeks ago it happened again and now it's a waiting game again. Then he asked me yesterday why don't I just get on birth control because he wants to cum inside me again. Now I don't know if I should get on birth control or tell him no. I don't even know if I want to keep having sex with him anymore. I have been having this mixed feelings about this for a while now since I told him that I wanted a real relationship with him and not just sex. He hasn't given me answer on starting a new relationship or not. It's starting to make me feel like I'm only around for sex and I don't like that feeling. So my question is should I stay and get on birth control or just end the whole thing and walk away from it?