It’s difficult to know as most STI can be there with no symptoms.
There are a few different STI that can be passed with oral sex so the only way someone would find out is by going for a test after the window period is up. The window period is the time between when a person comes in contact with a STI and when the STI will show up on a test. It has been 3 months so you are past the window period and it would be a good time to get a test if you are concerned.
Have a look at our “Know your chances” web page, it provides information on your chances of getting or passing an STI depending on how you are having sex.
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