don't know how much longer I can take this

So my boyfriend lives about 40 minutes away and this is the second time someone has spread a "rumor" about him since Ive known him (about 4 months). I got a text from a friend where he lives saying some girl is telling people she slept with my boyfriend in December (while we were dating) and he's asking her for nudes. I don't think he would do it of course and he's so good to me but.... it'd be so easy for shit like that to happen. We text and snap nearly 24/7 but I'm only there 1-2 days a week so how am I supposed to know what he does? He also snapchats a fucking ton of people. It's just so sketchy and I'm crying... why do people try and ruin a healthy relationship?? This sucks so bad. How am I supposed to know what's really going on when I'm not there??