After having sex on saturday night, all week i have had the urge to wee all the time but only little urine comes out. i also have pain when i urinate?

Urinary Tract Infxn: Regretfully, it sounds like you have developed a urinary tract infection which can occur as a result of sexual intercourse. I would recommend seeing your primary care doctor who can conduct a urinalysis and treat it. The treatment is relatively quick and painless--usually just a few days of antibiotics. Make sure that your doctor also checks for signs of an STD. Good Luck!