Does my dog have Cancer?

She has been losing alot of weight, she eats but doesnt gain weight, i just realize that she was losing weight couple weeks ago, She is also loosing more hair. She always sheds but this time she is losing even more hair. I took her to the Vet a couple months ago, because she had a seizure (just one time) the vet gave me pills and told me i had nothing to worry about. After she had the seizure, she hasnt been able to walk the same, she walks lopsided and has a hard time getting up. i dont know her exact age, we had her for 7 years, and we think she was 2-3 when we got her. I dont have any money right now to take her to the Vet. My friend said she could have cancer, but im not sure