Sexual compatibility? Is this a deal breaker?

So I've been dating this guy - who btw is anxious and a workaholic and has little time to build a relationship - but I've given him an opportunity because he is a good person. He has been making strides to understand what is needed to make the relationship work, BUT we've been sexually active for nearly three months and I'm extremely dissatisfied and I've made it clear what needs to be done. He thinks it is an area he can improve upon. He says I can "mold him", but I'm extremely skeptical because he hasn't improved in that area. Should I just cut my losses and move on or do I give this more time?