I had the exact same problem as you in my past relationship which ended a few years ago. The girl I was with had flawless skin. As for me I had a little bit of acne, but not too servere. Eventually i started to become obssessed with my skin to the point where i would cancel our dates. Acne was never a topic in our conversations. Its like she doesnt even notice it at all. Looking back at pictures of myself in the past I now realized that my skin wasnt really that bad. (Especially compared to now) The thing is I was too insercure to talk about it with her. I kinda just let it bottled up inside me. I was thinking of starting this conversation with her but days turns into weeks and weeks turns into months. In the end I could never bring myself to tell her. Eventually my insercurites costed my relationship. Till this day I still regret not having enough courage to spark that conversation. If i could go back in time I would probably man up and tell her. Maybe if i did we would still be together right now... Unfortunately i can't replay the past. Im not saying that this will happen to you cause chances are it wont. What i'm saying is dont let your insecurities get the best of you.
All the best.