I have no idea whether it is SDT or UTI. Sounds like UTI to me, having had lots of those with all the burning and running to the toilet, but if it hasn't cleared up with all the usual treatment, it is time to do something about it. I am afraid you will need to find the time to go to the doctor.
Can you go to an urgent care after work? They can easily test for a UTI and STDs.
An STD won't give you pain up near your rib cage, but it could certainly cause burning and urgency. I think at this point, you need to be seen no matter what the cause, because it isn't likely to get better.
It is VERY IMPORTANT that anyone who suspects they have an STI or UTI to get themselves checked out. Especially given the recent infidelity. Your husband should also be required to get a complete sti panel done and show you the results before resuming sexual relations. HPV, herpes, gardinella, bacterial vaginitis and others can all be transmitted by a male with no symptoms. In fact, men typically do not display symptoms.
For your own piece of mind, I would go to urgent care and get all the testing done.