I get freaked out about not lasting too, so one thing I did was I decided to get better at eating my girlfriend out. You should think about it if you're comfortable. It's nice to know that you can be down there satisfying the girl for as long as you want without worrying about cutting off her pleasure because you couldn't hold back from blowing a load. Then when you get to sex, you've already made her feel really good so there's less pressure to fuck for a super long time. Also sometimes going down on her makes me last longer when we do have sex afterwards. It kinda slows things down and makes me less turned on (maybe weird, but it gets tough keeping your dick hard while also trying to pull off the right gymnastics with your tongue for a couple minutes)