Yes, it's normal beahavior. Mollys are livebearers and males always look for some 'action' with females and will constantly pester them....(yeah, typical males right....

). It's for that reason that when it comes to livebearers like Mollys, Platys, Swordtails and Guppies, that they always recommend that you outnumber your males with more females. So, for every male molly, you'd want at least two females. This way, the males will still get distracted by the females, but he's got more than one to chase, thus allowing the other to get some occasional rest.
If I were you, and your tank could support it, I would get another female molly. Good luck!