Why does my libido go down for so long after sex?

Hi guys,

as many of you I suffered PIED.

So I didnt watch porn for almost a year, did no masturbation for at least 4 months now and experienced a lot of good effects (no brain fog, more motivation etc).

Since 2 months I have a girlfriend, which I told everything about my problem.
We had sex several times already. Thats great progress, but I still have some problems:

1. While intercourse my dick is only 85-90% erect. (Although sex is great otherwise)
2. Every time we had sex, my libido goes south for at least 1,5 weeks. So the days after sex I am not horny at all. Really frustrating!
Especially the first few days after sex I always experience some of the negative effects that I had when I was fapping (bad mood, little brain fog etc).
But these effects are not as strong as they were when I was totally addicted.

So do you think sex with my gf is benefical to the healing process?