What could it be?

In may i had oral sex with my boyfriend. Neither him nor I have any kind of STD. A few weeks later I noticed what looked like black bruises or discoloration in my lips. I went to the dentist and she said it could be maloma deposits of some sought. Last night I noticed tat the smaller black spots had gotten bigger and spread. I take good care of my mouth so I dont know what it could be. I have taken an HIV test recently that came up negative, been then again it has been 3- 6 months since contact. Do you think I have to worry that I may have contracted an STD?

[Vance2335]

You already said that he does not have a STD, then why are you worried about a STD?