please give feedback

so i got the nexplanon arm implant about 2 or 3 months ago. a week and a half later my boyfriend cums in me, and i got it inserted while i was on my period so it must be effective immediately. however i haven’t got my period ever since, and my period during the time i got the implant went on for like two weeks. (more like spotting i think) but i’m scared to find out i’m pregnant. i bought tests from the dollar store, going to check wednesday. my stomach feels bigger and i fart more... a little sore too. maybe i’m just overthinking. thoughts?