Back ache/pain. I can loose weight?

Hi..I weigh 73kgs and have back pain from 5Days. .consulted physiotherapist and much better now.. I want to know..That can I join gym for weight loss? ? Is gym will effect me because of back problem??? my dad also have back problem and had operation of slip disk..he advising me not to join gym... and if not gym..then by which physical activity I can loose weight ?? Till now..I have back pain three times. ..Firstly in sept 2015..den a severe one in November. ..I went to doctor and he said gap between two discs are reduced(lower disc) ...and he advised physiotherapy(attraction and vibrations for blood circulation ).. N now it's third time..but this time,it is muscle pull.. Please suggest me..I really want to loose weight