I feel unwanted/undesired

Whenever me and my girlfriend do it, we're always done when she's done. When we do it, it's always me helping her, and when she finishes, she leaves to go get cleaned up and that's that.

There is times when she says she'll help me afterwards, but she always seems out of it or uninterested after she finishes, so I tell her it's fine and we stop, leaving me to take care of myself later while she sleeps.

And as of lately, I've just been feeling unfulfilled, unwanted, and undesired, but as both the man and the older partner in the relationship, I feel like I don't get to say anything about it to her as it may come off as complaining and I have to be grateful or wtv for the time with her I do get..