(NSFW) How do I help my boyfriend to be able to properly clean his genitals?

I haven’t visited in a long time, and I am currently facing a dilemma which I thought was appropriate for asking advice for on here.
I hope I posted in the right section and such.

Some background info;
I’m in a relationship, for a couple of months now, with a 24 year old guy, who told me, that he has experienced something bad in his childhood.
This had to do with a woman sticking stuff IN his genitals, when he was a kid.
For the most part, this does not affect him in our relationship, or in his current life.

But, I have noticed that when he takes a shower, after he’s done showering, his penis still has the smell it did before he took the shower.
Also, during oral sex and sex, I noticed that at the bottom part of the tip of his penis, where all those little sensitive bubbles are, he’s extremely sensitive.
So I’ve been giving hand jobs. Which I think is boring, I’m like to give oral sex better. I want to be able to pull down his pants at random period times of the day, and give head. Which I can’t do at the time.
At the moment I’m on my period, so we can’t have sex, and normally that just means I give head more, but since he has like white shit, still from when we last had sex, which was like 4 days ago, after he’s had like 2 showers, I’m like.. ok, I’LL try to do it.

So we ware at my place, and I started playing with him, and noticed, when I pulled the foreskin back, that it wasn’t clean, but he showered this morning!
So I told him, when I stopped playing, that I would like to wash it, because I don’t like giving hand jobs as much as I like giving oral sex.
He agreed, and we went into my bathroom, I took a towel, and tried to wash it, but he didn’t let me pull the foreskin all the way back, and even when he did it himself he couldn’t pull it way back.
But there was like a massive amount right where the most sensitive part was, at the base of the head.
Then he started making noises like a kid that was sad that someone was trying to take its candy, and when we stopped he seemed on the verge of crying.. And then I remembered what happened to him..
He did cry, and I held him and told him I love him very much and care about him, and that I only want good for him. And that it’ll be ok..
I think that this must have reminded him of it..
A woman trying to do something to his penis that he normally doesn’t do?

But he needs to clean it.. One of the reasons boys are circumcised is because of hygiene. And it’s just not good to never wash there. If he would try to do it more often then he would get used to it but he doesn’t want to. I’m not going to suck a dick that still has dried up lubricant and fluids from me and him, from DAYS AGO. That’s just nasty.

So my question would be what can I do to help him?
He’s a really smart guy, so trying to manipulate or trick him won’t work.

Thank you for taking the time to read this.

Kind regards… a girl who desperately wants to suck her boyfriend’s dick..