so i noticed after sex with my longterm gf i had a red foreskin, plenty of lube so wasnt anything to do with friction but more of a reaction, cleaned it well after and woke up the next day to a dry foreskin that was a little tight, its now gotten worse and is splitting as i pull it back. ive googled and seem to come across balanitis
Your skin has had a severe reaction to something it has been in contact with: had you used that particular Lube previously? Was it an actual lube or something else?
If you have used the lube previously, say on several occasions without any problems then the likely cause is something else your penile skin was in contact with.
Try to think of everything that has contacted your penis after the sex took place, although it could be something GF had used, it is less likely.
So you say you “cleaned it well” - what did you clean it with, was it one thing, or a range of different things.
Were any of the things you did use different to what you have used before?
Is it even possible that there could be something like bleach or some form of steriliser has got mixed in, either deliberately or inadvertently to any of the cleansers - soap etc that you have used.
In terms of resolving this your penile skin needs time to heal: wash with water only, and dry it real carefully with a towel that only you use, so that no further damage is caused.
It will take an extended period of weeks for the healing process to actually achieve anything, and then it will need to regain the strength and resilience it once had - this would take 8, 10 or even more weeks to become strong again.
This is dependant on you NOT stressing the skin in any way, and this sure means not masturbating or having sex as this will simply delay the healing process to have the skin as it used to be.
Knowing what caused this would help, as you need to make sure you do not apply this to your penis, or that your penile skin does not come into contact with it again