You mention your mental health - are you in counseling? If you aren't, I hope you consider it. Your mental health is just as important as your physical health.
Performing oral sex on a vagina is considered low risk. The chances of getting are quite low. You could get oral gonorrhea, chlamydia or syphilis, though syphilis is uncommon in most developed countries, like the US, UK, Canada, countries in Europe, etc. The chances are low enough to not warrant testing, according to most experts. If you need to test for peace of mind, you can get an oral swab at 5 days for gono and chlamydia and a blood test for syphilis at 6 weeks.
Receiving oral sex puts you at risk for gonorrhea, chlamydia, syphilis, and genital herpes type 1, if you don't already have oral herpes type 1.
The testing times are the same, and if you feel the need to test for herpes, you can do that at 6 weeks. I'd honestly skip it if you don't get symptoms. The hsv1 IgG test misses a full 30% of infections, and it won't tell you where you have the infection - oral or genital, just that you do. At least half the adult population in the US has it orally, though most will never get symptoms (think cold sores), so blood testing without symptoms isn't always helpful.
Really, I think most important right now is your mental health. Please talk to your doctor.