Questions regarding STD's?

I am a teenage girl, and I've preformed fellatio on my boyfriend multiple times. We also had very very VERY brief anal (there was no ejaculation) which only happened once. Both of us have never been active before we met eachother, and I don't think either of us have any STD's genetically. I've gotten sick recently after giving, with cold-like symptoms: runny/stuffy nose, frequent sneezing, and lethargia. I've read up on if these could be symptoms for an STD, but I ended up even more confused. Could someone explain to me if those are symptoms, or if I should get screened for STD's? I plan on talking to my guy about using protection when we have oral, too, as a preventative. I'm sorry if this sounds like a stupid question, but I'm really lost. Thanks :)