SERIOUS QUESTION-BIRTH CONTROL/UNPROTECTED SEX

Hello- 
I've been on my birth control for about a year. I had reached the end of my pack, and couldn't refill for a few weeks. Then once I got it, I started it up again. Of course since being off it for even just a little bit of time, I had 2 periods. 
But, here is my question. On March 11th, me and my boyfriend had sex. He didn't use a condom, and he finished inside since I'm on my birth control, and I've had good luck prior. It's been about 3 days since, and I've been having cramps. A little more cramping today, also some gas (don't know if that's related at all) 
Should I be concerned and visit my OBGYN? I just started dating my boyfriend, about a month ago. I know it's not necessarily possible for pregnancy symptoms to start, but I just want to make sure! We are not ready for anything like that! That was our first time having sex, and I just wanted it to be special & intimate. 
Please, refrain from any kind of judgment. I'm 20 years old, I'm an adult! I just want to make sure what I'm feeling isn't implantation cramping. I've had no bleeding, just to toss that out. 
If anyone can help, I'd appreciate it!