Knee and right pelvic pain. Like before?

Hi, Recently I have started going to gym and its been 3 months until now. Everyday I spend to 1.5 hr mainly on cardio and full body workout. I am getting lot of knee pain (both) also recently my right pelvic area also giving pain when doing high knee or right leg stretch sometimes while walking . Instructor said its common and dont put too much pressure on knees. But i am worried a lot since its been 3 months but still pain is consistent while climbing stairs, jump, squats or sitting on a chair. I have to use my hand support to sit or to getup. Few years back I have practiced yoga and never felt like this. Seems like i made a wrong decision of choosing gym. Am i ? How can i get back my knees to normal state like before? Appreciate your suggestions.