Patella (kneecap) dislocation question?

I'm 15 and I recently (yesterday) dislocated my kneecap, this isn't the first time it's happened and normally when it does i just knock it back in place myself but I'm not able to walk properly for a day or two. This has happened about three times before. Should I seek medical attention for it? It slips out quite easily and normally my knee cap is very mobile. it doesnt mean it hurts any less though :/