Well mate, im in for a cruciate ligament reconstruction on Weds morning! If i were you i would be getting it checked out again before you do any more damage. Joe Cole's ACL injury started out as a tweak, 8months later still sidelined! I did mine in December, took a while to get through the consultations and scans etc but worth it i hope.
I would go back to the Dr's, they will send you to a specialist who will refer for an MRI i expect, safest way i reckon.
The hosiptal told me mine would be fine in 6weeks when i did it originally.....9months ago and not played a minute since!
Swimming kills mine, try some cycling, wont do any damage, 'in-line' activities wont do any damage, cross training is also ok