I decided to get tested on day 7th of post exposure, Gonorrhea Chlamydia negative and Syphillis both RPR and TPPA negative and HIV negative. 

However I am aware it takes 6 weeks for syphillis to appear on blood test as well as HIV,  

The clinic prescribed me doxycycline just for preventive on day 7th post exposure, I am on day 6 taking doxycycline it has been 13 days from exposure will doxycycline prevent me developing a chancre? Let’s assume the transgender that licked the tip of my penis and licked my shaft and wrapped her lips around head for 5-10 seconds max had a tongue chancre or lip chancre. Will I still develop a chancre or will the doxy prevent it from developing ? Even though I’m barely on day 6 of doxy and 13 days post exposure, I plan on taking it for the full 14 days. However I also wanted to know if I am currently putting my spouse to risk ? Can I be infectious without a chancre ? Can a chancre be so small that I can’t see it on my penis but still infectious ? My fear is that I can be infectious, But will never go on to develop a positive blood test due to doxy I’m taking but fear I may infect my spouse. Like I said I been looking closely and don’t see any sore on my penis.