You are freaking out just over having to go to the bathroom slightly more often? Needing to pee isn't a symptom of early pregnancy. Don't worry, just take a pregnancy test and then do something about your tendency to get so distressed over imaginary risks that you took Plan B. (I hope you aren't taking it every time you have sex in mid-cycle even when using condoms. Plan B is meant to be taken only for genuine emergencies, maybe once in a couple of three years, not on the regular just because you get nervous even though there was no condom failure.) My suggestion is to wait and see if you have actual pain, such as possibly a kidney or bladder infection might bring on, and/or start drinking a lot of cranberry juice to see if you can flush out whatever is bothering you.
So, getting UTI's after sex isn't all that common unless you are having fecal matter introduced to your urethra. Be really careful of that. This means not having anal and vaginal sex both without a wash off, not finging both with same fingers either. Sounds gross but this is basically how UTi's happen after sex. Gotta keep the back and front separate just like when you go to the bathroom.
I would not think you are pregnant after using a condom that remained intact AND taking a plan B. You can double check with a pregnancy test but expect it to be negative. But know that your period may be off and irregular for the next 2 to 3 months because of the plan B which messes with your hormones (how it works to prevent conception).
A bit more frequent urination can be a sign of pregnancy but don't think so in your case. good luck
So are you concerned that your pregnant, even while using a condom and Plan B?
Maybe you just have a UTI? Have you seen your doctor about it?
If getting pregnant makes you anxious (and that's understandable if you aren't ready for it or don't want kids), have you considered the pill or another form of birth control, along with condoms?