Please assess my risk for brief unprotected vaginal sex

[Hellomynameis22]

I got fully tested for all STI's including HIV almost 2 months ago. During that time I was sleeping with my "bf" unprotected but was routinely getting tested and even tested after our relationship ended. I was negative. However, a month ago I slept with this guy I met on tinder (my bf and I had stopped sleeping together). I've always used condoms when I slept with anyone else (besides my bf of course). During our "enagement" he preformed oral sex on me and also ate my ***. I preformed oral sex on him. We also had vaginal sex. We were using condoms just fine, but somehow we started talking about just putting the "tip in". So I let him, but only for a brief moment, I want to say 10-20 seconds max. Then I freaked out and made him put on a condom again. He told me that he doesn't have any diseases but I don't know when was the last time he got tested. I know that I'm stupid and I already have high pre-existing anxiety about HIV so i don't know why I even went along with it. I'm so anxious about HIV that I thought my bf had given it to me and I started developing what I assumed to be ARS symptoms (headache, extreme body aches, ect) but I tested negative. But with this encounter, I'm starting to freak out. I felt really tired for a week (2-3 weeks post possible  exposure) and I also developed a headache that hasn't gone away (I've had it for 1.5 weeks now). Plus I looked in the mirror and saw what seems to be ulcers in the back of my throat/esophagus. But I don't have a sore throat or cough. And I cannot stop worrying! I haven't had any swollen lymph nodes, fever, or rash... Yet. But idk if this is all anxiety or if I'm truly going through ARS symptoms. Please let me know my risk.

1. Although he was only in me for 10-20 secs, and he did not ejaculate in me, how at risk was this exposure?
2. Can you get HIV through pre-cum (idk if there was, I'm assuming)
3. I also swallowed his cum during oral, what are my chances of getting HIV through that?
4. Can stress/anxiety cause all these symptoms? (I'm worried about the spots on the back of my throat, I'm not sure if they've always been there)

[Hellomynameis22]

1. Although we had unprotected sex for 10-20 secs, it is still concidered a low level exposure? (We continued with sex for an hour protected)
2. What do you think caused the throat ulcers/sores? I also started smoking weed and idk if that caused it due to dry mouth. I looked online and it seems consistent with esophagitis.
3. I had also began treatment for BV with  inserting Clindamycin vaginally. Could the Clindamycin that was in my vagina kill the HIV virus if I were exposed to it?
4. I had been on antibiotics for several months (vaginal  Clindamycin and metronidazole (both oral and vaginal) could that have caused the what I assume are throat ulcers?
5. Lastly, how long should the spots on my throat last?

Thank you so much for your reply!

[JamesD1991]

1.  Yes, you had a low level risk.  
2. Yes
3.No need for testing.
4. Anxiety can create a wide range of physical symptoms.

Take a DUO test at 28 days and expect a negative.

[Hellomynameis22]

I'm not sure if the spots on the back of my throat are attributed to mild acid reflux, stress, antibiotics (I was taking Clindamycin vaginally for BV during the week i slept with the guy), or oral gonorrhea, or ARS. Please let me know