I've been having bloodshot eyes in the past few months they whent away but now it's suddenly back it's one eye and it hurts alot?

Eye red with pain.: What you have now may not be related to what you had before. Both eyes red, now one eye red with pain. Would suggest you see an ophthalmologist to exclude a foreign body under the eyelid or a corneal foreign body, abrasion or ulcer to start with.

Get it checked asap: Severe eye pain can be a medical emergency, especially if it hurts to move your eyes, or if you're having changes in your vision. Get it checked as soon as possible.