Can you get an std if neither partner has one?

[Sara14_]

I invited my guy friend over, at the time I was on my period and didn't plan on having any sort of sex. One thing led to another and we ended up making out for quite some time. He was being a bit rough and started kissing my breasts which led to him biting on them. I didn't notice any pain or bleeding until he left but I ended up giving him oral sex. When he left I noticed both my nipples were bleeding so I put bandages on them. It has been about 2 weeks since then and I have noticed white ulcers on my vagina and on the back of my throat. My nipples are not getting any better, I have been putting healing ointment along with bandages every night. My nipples are now turning white along with a yellowish puss. I have asked my partner if he has or think he has any sort of disease and he told me he does not have anything. I'm pretty sure it is highly unlikely to get an std from nothing so I don't know what is going on. When my partner and I were together my pants never came off, I am confused to why there are ulcers on my vagina. Please help.