Help!!! Potential pregnancy

Hi. I wanted advice on what I should do in my current situation. I've only had sex twice in the last month with my boyfriend (we're both 17) and each time used a condom and he hasn't cum inside me as I'm not on the pill. However, at the start of December we did have unprotected sex but he pulled out. I haven't felt any pregnancy symptoms until the last few days but now I have heavy tender swollen breasts, some back pain and I was very intolerant to alcohol recently. My last two periods both came, but my last one was more of a thick brown discharge with red blood spotting(only when wiped) and lasted for 2 weeks in small amounts. Any advice on what I should do next ???? This situation has stressed me out a lot as I really am too young to have a baby.