Every time you finish a relationship with a partner, you should go for a full std test before starting new relationships.
The kind of encounters you had with your ex-girlfriend (oral sex) would have exposed you to syphilis, gonorrhea and herpes. As you said, there is not really anything to worry about, because she tested periodically, which is always helpful. If you are worry about herpes, you can test 3 months after the last encounter. It would be interesting to test for the other two as follows :
-3 weeks after the last encounter, you can test for gonorrhea.
-6 weeks after the last encounter, you can test for syphilis, and if you get a negative result, it would be interesting to test again 3 months after the last encounter, as there are people that take longer to show a positive result.
All the best.