I would go back to prostitutes to have an experience with the uncircumcised penis but in a familiar setting. I mean - you are paying them, you are not raping them, so it is a fair exchange. You have two new things going in your life: your penis is basically brand new, and you want to have sex without paying for it.

Would it be smarter to do it one step at a time - first, build up confidence having (presumably safe, right?) sex with prostitutes. Having built up the confidence, start trying to find a female partner.

I do not know much about the range of services offered by prostitutes, but someone on here reported how caring the prostitutes were and how very educational the sessions with them were. They taught that young man many things and acted to remove what you call "complexes".

Now, this was reported on here and I do not know to what extent it was true, but it won't hurt to ask especially given that it won't be your first visit so you know the milieu and are oriented to it.

There is also what is called a confounding effect. you are analyzing your issues now and you have many "maybes" - maybe it is lack of experience, maybe it is this, but no you are not timid, etc. So if you deal with your maybes one by one, it will be easier to finally pinpoint the source of the trouble.