Ahem. 'Twas I who used the "unpaid whore" expression back there and I thought I was clear that I don't think that of OP. And I stand by my assertion that JerkWithBenefits probably did. So, please don't anybody lump me in with the Puritans.
I love a good FWB arrangement, or even a decent booty call, when it's done right. But it's clear he had too much "power" in that dynamic - I was struck by you saying he'd go off for months at a time, but I didn't get the impression you'd ever done the same, or would have.
I don't think he treated you badly because you exercised your sexual liberty, but because (as far as I can tell) you gave him no consequences for treating you badly.
Even if tou decide not to do FWB or similar anymore, flip it around in your head: the number of women who are are comfortable with that are far - far - fewer than men who want it. That makes you more valuable, not less. And any guy who doesn't get that you deserve better doesn't deserve your company of any activity.
Finally, oh, sweetie, you sound so broken and inevitable. You allude to being dumped by ExH for another woman (and he's still giving you grief), that you're not "allowed" to have a meaningful relationship, and that you don't think you'll ever be able to pick a good'un. May I ask, was ExH abusive as well as cheating? Have you considered counselling, Freedom Programme? Would you consider having this fred moved to Relationships? Plenty of non-judgey wise women there. 