I agree with Curfew, but would like to add that if you've given oral sex, and have an oral STI infection, you may have swollen glands in your neck.
Humans are notoriously bad at identifying our own swollen glands, though, and there are literally dozens and dozens of things other than STIs that could cause swollen glands in your neck.
If you think you have an STI, you should just test and find out. If you think you have swollen glands, get checked by your doctor. In the past, you have posted about symptoms you have for months without getting checked out. This is a great time to not do that again. :)
In your neck? Unlikely. A palpable lymph node could be caused by any infection, including a common cold or a tooth or throat infection, or something more serious like cancer. A palpable lymph node is way too non-specific to be used in diagnosis.
If you have been sexually active since your last testing, and you're concerned about STDs, you should simply test for STDs, but there's no point in trying to connect a lymph node to any specific infection of any kind.