Make an urgent appointment to see your doctor and take a urine specimen you (that is if you are not on your period now).
The symptoms that you describe are that of Cystitis. This is a bladder infection and is quite common after having rampant sex. It is also referred as the "Honeymoon Syndrome"
Make sure that you drink plenty of water - at least 2 litres per day but no more than 3 litres unless your doctor advises you differently. You need to keep drinking a lot to flush out all the bacteria. It will hurt to pee, but you must keep drinking.
To help ease the pain when you urinate, drink a glass of water with a teaspoonful of Bicarbonate of Soda (you can purchase this at our supermarket and also from the pharmacy). You can have a drink of this every hour for 3 hours maximum. What this does is to neutralise the acidity in the bladder that is causing the discomfort. Drinking fresh lemon juice in water will also help to neutralise the acidity.
Your doctor will prescribe the appropriate antibiotic to treat you.
Sometimes you can also pick up a fungal infection called Thrush, and the doctor will be able to prescribe antifungal medication for you. He may prescribe you with an antifungal cream and/or a capsule to take by mouth. Fungal problems can make your outer vaginal area and bottom sore as well as itching. If you have this, it is highly likely that your boyfriend has this too and he will also need to be treated at the same time as you, otherwise you will be passing it on to each other. You can purchase antifungal medications from the pharmacy and the pharmacist would be able to help you. For now though get seen urgently by your doctor.
To help to prevent the bacteria getting into the urethra (the pee tube), after sex go and have a pee even if you are not able to wash straight afterwards.
When you use the toilet to empty your bowels, always wipe your bottom from front to back to stop spreading any bacteria to your front passages. Always wash your hands after using the toilet.
Also ensure that your boyfriend has clean and washed hands after he has used the toilet and before he touches you.
It is a good idea to keep off the sex until you are well healed.
You could have a couple of different things going on here. First, if you did not "clean" up your genital area after having sex, you could have a urinary tract infection. That can cause painful urination, some blood being seen on the toilet tissue, as well as abdominal pain. To avoid any chance of that happening in the future, always clean up after intercourse and try your best to urinate after as well. That will help flush away any bacteria that may find it's way into your urethra and bladder. Typically, urinary tract infections cause the abdominal pain (sometimes even nausea and vomiting), urinary pain, occasionally back pain, and fever (if it is left untreated). You didn't mention if you still see the blood since that first time, so perhaps if none has been seen since it could be that a small fissure (crack) from the friction was caused either in your vagina or at it's opening (vaginal meatus). Second, you could have an STD that can cause slight bleeding after the friction of intercourse, as well as some abdominal discomfort. With either of these possibilities, a visit to your primary care physician will need to occur. Be sure to not go pee for at least two hours prior to your appointment with him/her so that you can provide a urine specimen when you go. Also, with either of those illnesses, if an antibiotic is prescribed to you, be sure to use it until completed, unless you have a problem with side effects from it such as bad diarrhea or bad nausea/vomiting. If you have that issue, you will need another antibiotic to replace it from your physician, and a phone call to the office describing the reaction and a pharmacy that you will be using so that a new one can be ewired or called in for you. Please do not forget that any time you are on an antibiotic and birth control pills at the same time, your birth control will be less effective, so another form of birth control (condom or foam or vaginal tablet) will be needed in case you have intercourse. Good luck!