As you are experiencing uncomfortable symptoms, make an appointment to see your doctor and tell him the symptoms that you have.
Bacteria and fungal infections can still be transmitted through having oral sex. If a person with a STD has active sores in the mouth, then of course there is the risk of getting infected through oral sex.
The symptoms that you are describing with the itching, is likely to be a fungal infection. But you may have picked up a different bug.
You need to get your urine checked for any urinary infection and a swab from the penis to find out if you actually have a fungal infection.
The other type of infection that you could get with similar symptoms, but symptoms are not always present is chlamydia.
Get checked out urgently, so that you can get the appropriate medication. straight away.
Don't allow anyone to touch your genitals without washing their hands first. Bacteria and parasites can be transmitted by contaminated hands. Mechanics who have contact with engine oil also pose a health risk (not STD). And should always ensure the hands are thoroughly washed when fishing their job.
Make an urgent appointment to see your doctor.
STD risk is low for oral sex. Symptom does not make me think of a STD, but you can always test.