Even if your lawyer is working on another case, they should contact you within a day or two at most. Your lawyer owes you responsive communication, even if you are not his only client. There's no excuse for a lawyer to take weeks to return calls or emails. Initially, it may take 2 to 4 weeks to get your medical history, and sometimes a little longer.
Once the lawyer has a set of your medical records, he should review them and send them to a doctor for review. It may take another 2 to 3 weeks for the doctor to review the medical history and discuss your case with the lawyer. In some cases, your lawyer may have a good reason why it took 4 to 6 weeks to evaluate your case and decide if he will accept it. If it takes longer than 6 weeks for your lawyer to evaluate your case, you should find out why.
Start by requesting a meeting or conference call with your lawyer. Ask your lawyer why you haven't made a decision about your case and how much time you need. Your lawyer could have a good explanation for the delay.