About 8 days ago, I had sex with a girl whom I haven't had sex with for more than 6 months. In between that period, I abstained. I don't know about her.

Last time when we got STD tested about 10 months ago, everything was negative but HSV was not included.

As far as I know, I never had coldsores, nor she did according to her.

However, I had slight penis pain even a couple days before having sex with her, but ever since then it's been hurting more. Could this be friction burn; or could I have had some sort of skin breakage that would make me more prone to HSV infection via fellatio?

I have been observing my genital area to see if I have any sores/blisters/discharge/etc.

I got so paranoid to the point where I have been observing my anal area as well. I found a fissure(ulcer?) on the anterior midline of my anus.

Should I worry about HSV1 - 2, syphillis, or some other STIs? Thank you.

Welcome to our Forum.  I'll try to help. 

The exposure that you describe was low risk for any STI.  You know your partner and know that neither of you were infected 10 months ago and that you have not put yourself at meaningful risk for STI since then.  Her risk, of course, is related to her behavior over the past 10 months but unless she has engaged in high risk behaviors, her risk of getting an STI over the interval is also rather low.  In addition, your genital contact was condom protected and therefor less risky for STI acquisition.  There is a slight risk of acquiring gonorrhea or NGU from receipt of unprotected oral sex but that risk is low. 

Please provide a bit more information about your penile pain.  Without lesions or sores, it is unlikely that this is herpes (HSV-1 - HSV-2 is virtually never acquired from receipt of oral sex) and if it were due to friction I would expect it to occur within 12-24 hours after sex and then to improve over the next day or so.  This is too early for syphilis to occur.  Does the discomfort you are experiencing occur during urination or all the time?  Is it on the inside of your penis or outside and does it involve the entire penis or just one area?  Is there any discharge that you have noted from your penis?

Nothing in your description of your recent sexual activity suggests that the anal fissure you noted is related to any STI. 

I hope this information is helpful.  I look forward to hearing more from you regarding your symptoms in the hope that I can be more help.  So far however there is little to suggest that the exposure you describe was high risk.  EWH