1993 Subaru Impreza Please help, not sure if mechanic did p

In April of 2007 I had my clutch replaced, the clutch was slipping prior to that for a couple of months and one day the clutch stuck to the floor. The mechanic replaced it with a new one(supposedly). After getting it back my hill holder was not working so I took it back to him and he admitted that he wasn't sure if he had adjusted it right the first time cause he had never worked on one before, well he adjusted and it was fine. About six months later I was driving and had a tough time getting into gears, the following day I stopped at a light and the car wouldn't move again, the clutch would go down and it would go into gear, just wouldn't move. Took it to the same mechanic and he said the clutch went again. I was so upset, he tried to tell me someone is driving it improperly which is not true( besides that I've been told no matter how hard someone is on a clutch it shouldn't go in 6 months) I paid 700.00 the first time and thats what he wanted to replace it again, I was just gonna junk it then a friend of mine called them and said I shouldn't have to pay full price again, they fixed it for just the labor, which was 200.00. Immediately after getting it back it would not stay in 4th gear unless held their. Then about 3 months later the car would stick and not wanna pull out on hills, it sticks and once gotten to a certain point would jerk and pull out. Then about a month ago it started making a winding/whistling sound while accelerating in 1st and 2nd gear. Also, 3rd gear started slipping slightly. Then the next thing it wouldn't stay in 3rd gear either. Now I can't get into 3rd or 4th gear, it just grinds and will not go in to gear! So I am now driving with just 1st, 2nd and 5th, not easy and I'm sure its not good on the car either. I do not have money right now to fix it, unless there is something cheap and simple that can be done about this I am gonna just junk it when it goes. My question is how long do you think I can continue driving from 2nd to 5th before the thing goes completely? And in your opinion do you think something was done improperly to cause this to happen by the mechanic? Or could this all be caused by something else, that the mechanic wouldn't have known about by changing it, that needs replacing. Could I possibly need a new transmission or is it definetely the clutch? Please any input or suggestions would really help with my plans on what I am gonna do with the car