Replying to Lower back injuries

So last March I twinged my lower back while riding around in the slush. When I got it checked out the doctor said it was only some muscle soreness and it was nothing to be worried about. Now I've been skiing 6 days a week and I've been experiencing the pain again mainly when sitting down or standing up. Has anyone experienced this before? I'd like to avoid taking off work and where I'm at right now, healthcare is very limited.