Can I still be pregnant?

I’m 25, I know the answer is yes. But what’s the probability? My boyfriend and I were out if the country and we had unprotected sex a couple of times. One of those times I really felt the need to get plan b, but it wasn’t easy to access in the country that we were in. So I got it when we were back in the states, although that was five days after the matter. (I know, you have to take it 3 days after at the latest)

Anyway, that happened exactly a month ago today, & I got my period today... I was literally about to go buy a test. I have however had sex with him ever since then. But I’m not on birth control. Yet. I’m setting up an appointment to try and figure out which is best for me. (I’ve only tried the pills before)

Anyway, I guess what I’m asking is, should I still buy a test? I haven’t had any symptoms but I do have a weird feeling in my lower stomach. Kind of when you feel anxious. (So that may be it?) other than that, I’m feeling perfectly “normal.”

Addition: *Lately I’ve been having my period at the end of the month. & it’s the 10th so technically I’m late. But my period does seem to change when it comes once in a while. It’ll stick to the same schedule for several of months & it will randomly change here and there. But not too often.