Bowel cancer

Good evening,

I have just come home from the hospital a week ago after having open surgery to remove a large tumour, part of my colon, lymph nodes and to be on the safe side per my surgeon, my ovaries and appendix. 
I have asthma so I called my GP to book my flu jab but he said I need to get stronger first, how long do you think I should wait before calling again?  Everyone around me seems to be coming down with a bad cold or the flu and this is the last thing I need at the moment.  Is my immune system low?  Sorry about the essay but I just seem to be worrying about everything at the moment. 
thank you for reading

sharon