I Have Been Trying To Get Rid Of Cellulitis Since

I have been trying to get rid of cellulitis since January, 2016 in my lower left leg. ER wanted to admit me, but my husband was dying and I needed to take him home the next morning. He died 3 days later. the infection didnt heal, and I returned to ER, where I was admitted, and put on IV vancamyacin 1.25grams, I went each day for IV infusions of vancamycin , and still not healed. anyways after several months of treatment with antibiotics it still hasn't healed. tonite after shower my leg looks so red, is swollen and tender . I was given doxycycline hyclate 100mg tabs a few weeks ago, but I had not taken it. I am 76 yrs old. and have RA, fibromyalgia, and other age related illnesses. do you think it would be safe to use this medicine for this infection? excuse my typo's, I am just too tired to correct them.