It's a good question. And pleasing to see a problem that I think only plagues PUAs at a relatively advanced stage.
I can't ascertain the root cause of your issue from your post alone - it could be due to a number of or combination of factors.
But I had similar problems (and sometimes still do) in the past. Four things that helped me:
-Play solid game; you know you can lay them quickly, but why? Let your dick have a night in and lay them on the day 2 instead.
-Show vulnerability. Don't be
too perfect (or too smooth?).
-Show genuine caring. Not sure how I do this exactly but it's helped me keep the right vibe in my MLTRs; I wouldn't recommend this for people starting out because I think it's useful to go through the 'badboy' phase to learn certain mechanics, and they may get friendzoned too early. But at your stage, and certainly I have found - to genuinely care about the girl really helps. Just giving them occasional compliments, wishing them sweet dreams, good morning etc.
-
Manage expectations!!!
The other thing is, girls should not be spreading bad things about you, even if you lay like a lawn mower out of control; they should be recommending your services to other girls. This is very important in the later stages of the game (at least I have found). If the girls who are spreading bad words about you are burnt sets - then fair enough - your game just wasn't tight then. But if they're previous lays, you didn't manage expectations properly.
Edit: I would add one further thing. Have you ever wondered why some "badboy" players who don't give a shit about girls never get branded as such? And they never have a shortage of girls? I have. I think it's because they are congruent with what and who they are. And again, this comes back to managing expectations. It is clear to a girl, when they meet these type of guys, what they are after. So they know what they're putting themselves in for. Once you become congruent, natural, and OK with being a laying machine...it's all gravy

.
I think to some extent, depending on if you are part of an institution like a college or a closed social circle, you will always get bad rumours; but that's just the life we choose live!
xxx