First of all I do hope that you regain your health soon
In reguards to your question it would be nearly impossible to find out if your illness is due to bad kamma or not. Kamma is very complex and only those who have developed certain meditative abilities are only able to work out what is the result of kamma and what isnt (in fact i think only the buddha could do this but i have a feeling i am wrong on this).
Illness can be a result of past kamma, but it can also be a natural occurence (for want of a better word) of life This includes all of illness from colds to cancer. It is this bodies nature to decay and become ill, even those beings in the human realm with great wholesome kamma are not an exception to this rule.
Either way it does not matter if it is the result of past kamma or not. Reflection on the illness in terms of impermenance, dukkha and not-self would be benefical. We are all subject to illness, we will all experience it, if its due to past kamma or not.
I hope this has helped answer your question