pill and problems

Right I've been on the pill now for a month with no problems!  Yesterday I had a pain on my calf at the back. The pain only occurred when I started walking.... it affects me more when I walk. It's hard to describe the pain but it feels like a bruise sort of pain. Some people I have asked have said I should get it checked out as it could be a blood clot due to the pill. I was just wondering if anyone has any more advice.