What happens if you've beat the Dawnguard storyline as a vampire and you've maxed out vampire lord - but you eventually want to try and find a cure for vampirism.. If you become a vampire again do you retain the vampire lord perks or are they lost forever? Is there a way to cure yourself and then become a werewolf if you've already completed the Companions?

Yes you can lose vampirism, hang around Morthal.

You do keep the perks once you unlocked them even if you lose your vampirism. Vampirism you can always get back

You can get lycanthropy once more after the Companions quest line.

If you want to switch from VL to WW then just talk to Aela. It will remove your vampirism and replace it with lycanthropy.

edited.

Is it a one time thing with Aela??

PS TTHANK YOU

I hope not...

Yes. Something along the lines of "Hircine doesn't not bestow his gift many times." Basically this is your last shot don't screw it up.

Wow, that's sorta harsh lol

But thank you...

If they fixed Vampirism a little bit like making it easier to feed or a way to just BUY the blood potions or something, it could be easier but I'm tired of every single place I go I have constant negatives in all of my stats for some reason either sunlight or hunger or both at the same time.

You can work around the negatives easily. You get completely used to them eventually.
You can do the Side Quests for the Vampires to get Blood Potions. I have like 40 of them, only ever used one just to try it out.
But yeah, it becomes second nature to you eventually.