Can Titer Increase During Treatment?

Hi doctor,

i was exposed about 60 days ago. I tested at week 5 and my vdrl was 1:16, tpha positive and my hiv test came out negative. I then started my medication for syphilis. I was given a penicillin injection and then doxycycline tablets(2 per day) for 2 weeks. At the end of the 2nd week I was given another penicillin injection and more doxycycline tablets for another 2 weeks. At the end of the 4th week I went on to do a blood test on my own at a private medical lab. This is my 9th week since the exposure. My test results came out negative for hiv and vdrl was 1:32. I was shocked with this results!! I checked with my doctor and he said that I should wait atleast 3 month to see the difference in the titer. My questions:
1. Can the vdrl titer increase at the end of the treatment? Or is the increase something I should worry about?
2. I read in some wesites that hiv infection can cause syphilis treatment failure. Could this be possible in my case?

I would really appreciate if you could respond to my queries soon! I am extremely worried.
Thank you!