Confused teen..!

So I had sex 2 times in one week( this was about a month ago) and the last time I had sex I was on my fertile days but just a week after that it seemed like I was on my period but I only spotted for 4 days. But we used a condom and I had just gotten off of my birth control about a week before that. Lately I've been eating and sleeping a lot. I'm late 16 days, well that's if the second time I had my period was actually a period. My boobs are tender but not as much but my nipples are hard is that weird or is it just me!? I have this pain on my lower back but only to one side, and I smell food all the time. I'm just curious could I be pregnant or is it just about the time I start my period again!?