Some articles would advise you to talk with your gf about the sex life. This tip sucks big time. She would probably feel like you are harassing her.
A much better option is to just have fun together doing some extreme and adventurous stuff.
What to do?
First, watch some sexy sex movies together with your girlfriend. Try to pinpoint things that you like and want to try out yourselves.
Second, take out of the bedroom. Have sex in the forest, in the car or near the car in the night. All of these adventurous activities will produce lots of oxytocin, dopamine and adrenaline, making you both lust each other a lot.
Third, consider buying some sex toys and flavored lubricants for oral sex. This will bring more diversity and variety to your sexcapades, turning them into more fun.
Everybody loves something new and just fucking your woman in the missionary positon for years won’t do any good to your relations.
And don’t forget about being sweet and flirting with her from to time. This will surely set up a good foundation for amicable and friendly relations. And more sex, as a result.