king snake not eating & has developed lumps

Question
hello,
i've been given a snake by my friend because she thinks it's
going to die, and thought i could do more to keep him alive
than she could.

problem: snake hasn't been able to digest food for about six
months.  he's also developed a lump about about an inch back
from his head in the last three weeks (but it hasn't changed
in size since i noticed it).

habitat: his cage has a gradient setup with a water dish on
one side, a hollow branch in the middle, and a heat lamp, a
half log and a heating pad on the other side, kept at
healthy temperatures.  i keep him on newspaper.

feeding history: my friend would feed him frozen pinkies
warmed by soaking them in hot water... which i thought a
little weird, so i tried live pinkies. the thing is, he
eats, but he just can't keep the food down for more than a
day. most of the time he refuses to eat, but i think he gets
really hungry and eats against his better judgement
resulting in regurgitation of his food :( i wait for his
stomach acids to go back to normal before attempting to feed
him again, but never get any different results.

medical history: before my friend gave him to me, she took
him to banfield pet hospital where they told her to give him
an injection of Baytril (?) every other day. i have no idea
what that is or if they just gave it to her cause vet
clinics usually don't deal with reptiles and didn't know
what else to do. (and as far as i could tell the lump
appeared after she began administering these injections).

please help! i don't want this snake to die...

Answer
OK, Baytril is an antibiotic and it DOES causes major damage near any injection sight.  I would recommend the vet do either a fecal float test (if the snake is still pooping) or perhaps a cloacal swab to check for parasites.  Parasites are more likely to cause what you described vs. bacterial infection (which is what Baytril is usually used to treat).