Should I quit my job?

My husband was diagnosed with cancer in Nov 2009. I went on FMLA the first three months, and when I returned to work in March 2010, I had horrible anxiety attacks and had to start taking pain meds and anxiety medicine. I had to miss a lot of work due to his illness, then in June I took another extended leave of absence and I'm still off. I am supposed to go back to work, per HR on Feb 1, which is tomorrow. For the past year I have had difficulty with sleeping for which I am finally on meds, cant sleep without them, prescrip pain medicine, and anxiety meds. I have crying fits, irritable and unable to handle lifes daily challenges. I do not feel that I can our could continue to work due the level of anxiety, etc that I'm going through. I have asked for so much time off due to my husbands illness I feel that I should just let the job go and resign....plus I have pressures from family members telling me I stupid to quit the job. I don't know what to do.??? its causing me so much anxiety. Thanks for any help.