Yeast infection? Cause my irritation?

I am 19 years old and have had no severe medical problems. However, I did have strep throats about 2 weeks ago and was taking amoxicillin for that but didn't finish the entire prescription (which I know is bad). I haven't had sex in about 3 weeks. I also got a really bad sunburn last week and took a bath that had 3 cups of oatmeal in it (I heard that helps with sunburns) which maybe could cause my irritation? Anyways since about 2 days ago, my vagina has been extremely irritated and itchy. I feel it might be a yeast infection but I have no thick discharge and nearly no stinging when I go to the bathroom. The irritation is right near the vaginal opening and go towards the back too. It is really tender and painful and don't know what I should do help me please! Thank you!!