Help! Is it possible that I’m pregnant?

I’m 16. I got my first birth control shot in February on the 21st and the estimated time for me to go back to get another one is may 10-24th. We have had sex a couple of times recently (ashamed to say without a condom) and I’ve been getting really anxious. What if I’m pregnant? He’s always pulled out well but I know pre-ejaculate can get you pregnant too. The shot has made my period really funky over the past three months and I’ve been spotting on and off a lot. But it’s stopped recently and I don’t know if that could be a sign? Along with a feeling down there. It doesn’t necessarily feel like cramps because it doesn’t really hurt, it just feels like something. If that makes sense? Sometimes I think it’s just gas that I might be feeling or my bladder, me needing to go pee. I’ve heard that you can get cramps and stuff after sex too, I’m pretty tiny so I thought that could be it (4”10 and 100lbs). And I’ve heard that when you are pregnant your discharge increases? But I really haven’t had any recently. I’m still really nervous. I know I should probably just get a pregnancy test, but I really don’t have a lot of money for one. And I don’t want to go to my mom yet, just cause I don’t want to freak her out. I don’t know. Just any advice or tips?