Implantation bleeding or ??

So I really need some help and I hope you girls can help! I don't want to give my hopes up and it turn out to be something else. My last period was May 9-12. Glow says my most fertile day was the 21st and we had sex. The only day we missed sex this month was the 20th. And Thursday last week I started spotting lightly and was a pink color and at times darker red. It lasted till Monday. On Sunday while I was working it got a little heavier than just being on toilet paper after I wipe and was in my undies. It seemed like because of how much I was moving it got a little heavier. Do you think this is implantation bleeding or could it be something else? My next period isn't due till the 5th of June. We have been trying the last 2 months. Last month I was so disappointed when I got my period and I just don't want to get my hopes up. What else could it be if not implantation spotting? I'm not stressed anymore than usual.