Q: When we used to have casual sex it was great, but since we became a couple I think the sex just isn't the same anymore. Why? Could it be that then we didn't see each other so often and sex seemed better to us?
Answer: There can be thousands of reasons! It may happen that one of you may have a lot of work, the stress affects badly. There may be health reasons. But also due to the fact that this relationship is no longer something new. When a relationship is in the beginning, there is more lust. This is undeniable. While seeing each other often is nice, that doesn't mean every aspect of your relationship will improve in a linear fashion. Sometimes proximity makes you notice things you don't like.
Remember that 'passion' at the beginning of the relationship is nothing but anxiety. Questions on your mind: 'Will he want to go on a second date? Should I invite him home? Will he think I'm desperate?'
Once these questions are over and you both agree that you like each other, the anxiety level will drop and many people take this as a loss of passion or a lack of chemistry. But no! Simply, the novelty is spicier.
In the beginning, you probably didn't have to adapt much to each other's unique desires. Basically, you can engage in various activities and get excited; discovering a new body is exciting. Experimenting and trying new things was easy because everything was fresh and unknown.
Now, you should talk openly about your desires and what excites you. What about exploring new experiences? Watch adult movies together, experiment with sex toys, have sensual massages, engage in mutual masturbation or exchange intimate photos. Don't forget to flirt!
Allow yourself to enjoy the ordinary! I'm not advocating bad or forced sex, but it's okay to have mediocre sex every now and then. This does not mean that there is no love or romance. Not every book you read will be your favorite and not every time you have sex will be the best.
If you keep having sex and keep talking about it and exploring, I guarantee you'll keep enjoying it and the desire for your partner will return. But it will also leave. Sometimes you feel bad about your body or you have a family problem and you don't want to have sex.
Sometimes the 'key' is to be patient and trust that everything is a phase , and to quote Rilke, no feeling is final.