I do think those that enter FWB situations can be rather naive. The long term ones are usually part of a male's life time harem.
The time frame suggests you have been a convienient sex partner, he supporting you in practical terms and you offering him sex, with no strings attatched, a fair exchange.
These mutually beneficient relationships are often viewed by females as very respectful, truths are often not spoken, because a different type of truth exists, the truth of sexual expoits, but more often than not these females are not involved in the real truth, that being the males usually have many concurrently running FWBs and F Buddies, that are concealed. Sexual health is ignored sometimes on a gigantic scale.
And they view these men as friends.
Both parties may aknowledge the existance of other partnerships, theirs is a shared secret in many cases, they are above the normal restrictions of primary relationships and the contracts that exist between equals.
There are advantages and disadvantages to these unions, but the one thing that really separates real relationships from FWBs is the false respect that has to be maintained for men to continue having 'free sex'. It seems he has noticed you have changed since your last meeting, have gained weight, are less confident, this has brought him less validation whilst having sex with you, you are now on the disposable list, the false respect has been erradicated.
He may have other FWB's who he supports practically and emotionally, your offerings may not be as essential anymore, he's basically done the unthinkable and shown you his real self, which is the death blow for FWBs.
He was always capable of this, you know that, but both of you extracted from it what you needed. I'm sure that in his primary relationships he was vile but your agreement was he would not be nasty to you.
This must be very painful but I believe he did this purposefully, you just have to figure out why.
So now you know he has always been judging you, maybe he has had enough of supporting you now and the sex no longer equals the fair exchange he signed up for.
I'd run if I were you, if you forgive this you will both know that you have seriously lowered your bar beyond offering sex in exchange for friendship.
He was never a real friend, real friends do not have sex.