Is your girlfriend the one you posted about the other day, or do you have multiple partners?
If it's just her, get tested for gonorrhea, chlamydia, syphilis, hepatitis B (if you haven't been vaccinated), HIV, and if you can, mycoplasma.
If she's not current on her pap smear and HPV test, depending on her age, she should get one. There is no test for you for that.
You can get herpes testing, but in many countries, there are not type specific tests, and if either or both of you get a positive test, you won't know if you have type 1, OR type 2, OR both. It's almost pointless to know.
If you can get a type specific IgG blood test, do that.
Make sure that you are within the appropriate time frames for each test -
gonorrhea, chlamydia, and mycoplasma - 2 weeks
syphilis and herpes - 6 weeks
HIV - 4th gen DUO test - 4 weeks
Hep B - 90 days
If you are not monogamous, you can test, but don't stop using condoms.