I have been having testical pain for the last couple days and I just took a shower and felt around and the vain connecting to my left testical is big . What should I do about it kind of freaked out about it

If this is a concern, the only option is to see your doctor.

I would see a competent doctor asap, if you don't have one go to the local ER to be evaluated. http://www.emedicinehealth.com/testicular_pain/page2_em.htm

Can I still masterbate while I have epididymitis .

You should refrain until the inflammation is gone and you get the all clear from your doctor.