Thanks for your consult at DoctorSpring.com
Let me address your questions in the order in which you have posed them.
1. UTI seems more likely. The reasons being
a) You have used the birth control meticulously
b ) Pregnancy resulting form unprotected sex WHILE you are having your period is unheard of.
c ) The symptoms began just 5 days later, too early for pregnancy symptoms to start in such earnest.
d ) Sex during periods is always slightly messy, more so because of the hygiene issues you must have had due to the change of place, and so UTI is even more likely.
UTI is generally characterized by painful or burning micturition, however it is not the norm. Frequent urination, mild fever, back pain are all indicative of UTI all the same. Moreover, the doctor ( albeit, Jordanian ) made a diagnosis, so it has to count ! The nausea and aversion to food is typical of reaction to antibiotics used to treat UTIs. So I would really say UTI seems more likely.
2. You can take a pregnancy test reliably IF and WHEN you skip your periods. Since you are on birth control, cycles would be regular. If you skip a period, take a test, do not stress out unless this happens.
3. Pretty much everything is confused with pregnancy, till you have a positive pregnancy test !! This is because early pregnancy has a wide range of unpredictable symptoms. Ranging from nausea, fever, fatigue, discomfort, food aversions, abdominal pain, breast tenderness.. you name it and you have it as a pregnancy symptom ! It can be confused with UTI, mood swings, pre menstrual syndrome, everything in the book. So do not read much into your symptoms. We can safely presume it to be a UTI as all points go in favour of a UTI instead of a pregnancy. Till a test is positive, assume you are safe.
4. Yes, good quality birth control is 99.9 % effective, so I can use the words - " you seem to be freaking out ' :) This does not make you an oddity, because any sane, responsible and normal person would. However, as I said, if your periods get delayed, only then do you come close to entertaining the possibility of a period.
The UTI has already been treated ( I hope a urine examination test was done and antibiotics accordingly prescribed ). Give yourself a few days for the effects of the antibiotics to pass off. Drink plenty of water. Meanwhile, have protected sex ( if you must ) to ward off any superadded infections.
Wait and watch for your period. Am pretty sure you will have it on time.
All the best.
Please feel free to discuss further.