Me and my boyfriend had sex last night, today it hurts to pee. I've been drinking lots of cranberry over the last few days, could it be a UTI or not?

Possibly. Typical symptoms of a UTI are burning with urination often associated with urinary frequency, urgency, voiding small amounts, and occasionally blood. Common after sexual activity. If a uti, may clear with increased fluids though usually 3-5 days of an antibiotic required. Benefits of cranberry juice/capsules controversial. If symptoms persist or worsen, recommend call or be seen by your md.
Could be. Some pharmacies have pee sticks. You can dip the stick in the urine and it can tell you if have a possible infection. The best advise is go to the doctor for assessment.