Pregnant on the pill? How can you tell?

So my last "period," about 2 weeks ago, came about 4 days early while I was on my hormone pills still. It came right after my SO and I had sex. At first I thought it was just from the rough sex because it was spotting. But then the light spotting went on for 3 days and then stopped. Then during my sugar pills I didn't get a period at all. I didnt think much of it until now. I had a little bit more spotting the past couple days, TMI but chunky and brown. It also stopped. I take my pills super religiously so I dont think its breakthrough. For the past few days I've been crying erratically and irritable x1000. I feel off, totally not myself. I've been sleeping/exhausted a lot. I slept 14hours yesterday evening/last night. I'm starting to get suspicious that I may be pregnant. I'm going to buy a test today I just wanted to see if anyone has experienced pregnancy on the pill and if it was harder to tell because of it. I did the math. I'd be about 7 weeks if I was pregnant. Thanks for any input. I appreciate it.