When the message pops up that my blood boils in the sun and that i'm growing hungry for flesh (i cant recall the exact words) .....
How do i stop the vampire transformation and why is it that i'm turning vampire?

I want to be a normal human and i thought that when i turned down Serana's father for the offer to become one of them, i wouldnt have to worry about becoming a vampire. I know this is a broad and stupid question, but i just dont get it and i want to know if there's something i can do about my sensitivity to light and flesh-hunger.

You turned down becoming a vampire lord that doesn't mean your immune to infection from the regular vampire strain. You probably got infected fighting normal vampires. The normal infection process can be stopped by taking a cure disease potion or praying at a shrine. If its progressed to full vampirism then you need to be cured by more complicated means.

thanks alot. i dont think my Cure Disease potion worked so i'll try the Shrine.

If cure disease didn't work then its progressed to full vampirism in which case you are the undead and require more complicated assistance.

Yeah, you need to leave for Morthal and see the mage there if you got turned into a vampire.

Okay, so first i tried Cure Disease Potion and that didnt work - neither did going to a Shrine and being blessed by it.
So i took your advice and went to Morthal where i found Falion (who i'm assuming is the mage you are talking about cuz he is the ONLY one there in mage robes. There is no dialogue options offering me a chance to be cured and i'm still infected! Any advice now? I'm at a loss.

I hear there's a bug to have all the side effects of vampirism with none of the powers and no curing in the dialogue xD
svcks but sounds like you got it lol

Kind of like the invisible bounty bug where guards attack you but you can't pay them off or submit to go to jail? You got an invisible vampirism bug.

I'd suggest trying to become a werewolf, then keeping it for a while to have the 100% disease immunity.

Try talking to An inn keeper in morthal to activate the quest ask about rumours

thats not what i wanted to hear but thanks for the info. you actually answered my friend's question too. he is pissed off that the guards attack him with a bounty that he cant pay off and cant serve time for. you described his situation exactly.

you could also become a werewolf as that cures vampirism and there's no effects except you no longer get the well rested bonus

This. But try talking to an innkeeper first. That should trigger it.

If you turned down Harkon's offer, then the Dawnguard should still be on your side. If you speak to Isran while infected he should direct you to Falion and start the quest too (at least he does with vampire lord vampirism. Not sure if it works with regular vampirism).

Get a black soul gem and go to mortal and have the dude do the ritual on you.

Cheers

Sounds like your best bet is to become a werewolf. There are few downsides and if nothing else you can just get cured.

thanks for the advice. you and some other people steered me in the right direction. went to Morthal Inkeeper, asked bout rumors, went to mage, met him in the marsh and he did ritual on me.
What i still don't understand is HOW in the WORLD does ANYONE figure this out unelss they ask on the Skyrim Discussion Forum or talk to every single NPC in the game until they get to the Morthal Inkeeper?! Maybe there are other ways as well but most people know this one. I dont know.

But i'm glad i'm cured and it wasnt all that hard... thanks to you all

You can talk to any innkeeper in the game and if you ask about rumors when infected with vampirism, they will direct you to Morthal.

There is indeed a bug that causes you to become a "want-a-be" vampire which is caused by Serena. Happened to me also, and I was a werewolf at the time it happened. There are no yellow eyes, and no cure. The 1.7 patch that came out fixed that. I was lucky that I had a save before I turned, but I still lost about 4 levels. All you can do is go back to a save "before" you turned, or start a new character. If you talk to an inn keeper an it triggers the quest, then great. If not, then find a save or re-start. Hoped that helped.

If you run around with Serana she's prone to giving you Sanguinare when she uses her Drain spell thing. Other than that you must be fighting hordes of regular vamps.

Either get Lycanthropy or go to Morthal to cure it.

Unless you become a wolf or find an amulet of disease immunity then there isn't anything you can do about preventing vampirism. Just keep checking your Active Effects.

Those amulets or rings which give 100% disease resistance are useful blockers of vampirism and other diseases.
They are pretty rare though