You're asking yourself "how to have better sex with my girlfriend?" You love her and you want to make her happy. Your motives aren't entirely altruistic though, the sex could get better for you too.
- Experiment with her. Chances are, if you're trying to figure out how to have better sex with your girlfriend, at some point you've asked her if there's anything she'd like to try. Not all women feel comfortable asking for stuff in bed though, some girls are very shy. You can help her to get what she wants by trying new stuff and asking her "Is this okay?" or whether she likes whatever you're doing while you're already in bed. That way, she can just say yes or no instead of having to describe to you what she wants. You may even help her to discover a new like. Go slow, though, so you don't accidentally make her do something she doesn't want to do.
- Tell her what you would like. Don't demand a blowjob. That's just obnoxious. Instead, tell her it would really turn you on if you could whatever. She may not be doing things you like because she has no idea that you like them. You can have better sex with your girlfriend if your girlfriend knows what you like.
- Stop whining. If you asked your girlfriend to do something she's not comfortable with, respect her boundaries. Not all women want to be porn stars. How would you like it if she was constantly trying to force or guilt trip you into having sex with another man in front of her friends or something you're totally not down with? You're not going to have better sex with your girlfriend by making her miserable in bed.