If you have to squeeze to see a discharge, it's not really considered discharge. Discharge from an infection (STD or not) will be there whether or not you squeeze.
So receiving unprotected oral sex puts you at risk for syphilis, genital herpes type 1, gonorrhea and NGU.
Syphilis isn't that common, and your partner would have had to have a sore in their mouth to transmit it. You wouldn't see symptoms of this for 10-90 days, but the average is 21 days, and you'd get a sore called a chancre. This doesn't cause burning, pain, discharge, etc. You can test for this at 6 weeks. If you get symptoms, but test negative at 6 weeks, test again at 90 days.
If you don't already have herpes type 1 (think oral sores, like cold sores but not canker sores), then you could get genital herpes type 1 from receiving oral sex. This can happen even if the person performing oral doesn't have a sore, but it's more likely if they do. The time from infection to symptoms is usually 2-12 days, but the average is 4 days. You can test for this now, and then again at 4 months to make sure you don't have it. If you test positive now, it's a pre-existing infection that you had before this encounter. About half the adult population has this, and 90% don’t know it.
You'd see symptoms of gonorrhea at about 2-5 days, and this would usually be a discharge, burning, etc. Some people don't get symptoms. You can test for this as early as 3 days, but 5 days is better. You can have a urine test or a swab test.
NGU is an infection in the urethra that is caused by anything other than gonorrhea (nongonococcal urethritis urethritis, sometimes called NSU, for non-specific). This can be caused by normal mouth bacteria entering the urethra, and the symptoms and testing times are the same as gonorrhea.
Receiving oral sex is lower risk than unprotected vaginal sex, but if you are concerned, you should test. You don't need to run out right now and test, but if you notice symptoms, definitely get to a doctor.