I’m on the combination pill and recently I have been bleeding after sex everytime. It’s just a small amount and having sex is often uncomfortable. Is this a sign of anything serious

If you aren’t using lube its possible you are getting tares.

Sex isn't supposed to be uncomfortable. As said above you're probably not aroused and lubricated enough so penetration is causing small tears and bleeding. It's not serious but make sure you are getting enough foreplay and using lube so that you're fully relaxed and aroused so sex can be safe and enjoyable.