I took the swine flu shot last week and have developed muscle wealkness,i am also taking omnicef.?

I took the swine flu shot seven days ago and was feeling ok until a few days ago when i stated feeling weakness in my joints.I was also given a prescription for omnicef at the same time.I would think that it is the omnicef that is giving me the muscle weakness.I was reading the side effects and muscle weakness was one of them,The strange thing is,it is also seven days later since i started the omnicef.Can the shot or the omnicef giving me side effects 7 days later.Like i said,i would thing it is the omnicef