Intercourse, this month period was a little bit late

Okay, I'm 15 years old and maybe around 6 months ago I had sex for the first time and we used protection and stuff but at one point he tried to do it without a condom and I got off him before it went in lol. He never came while in the act but he finished himself off. This question has been in the back of my mind ever since it happened, I'm ai pregnant? That month my period was a little late but I've had them these 6 months, this month I noticed I gained weight but than I went to new Mexico and I ate a lot so I'm thinking I could be big because of that. Also the day I had sex I went to a basketball game and played and afterwards I had a smoke and I noticed my breath was short and on the way back I was so exhausted. My breasts have gotten a little bigger and when I suck in I used to have a flat stomach but now theres a little bump at the end of my stomach but when I flex my stomach muscles it flexs, I'm kind of thinking its muscle because I've been working out a little. It barely makes sense but please give me some honest feedback of what you think?