Slow Cable Speeds, unknown problem

Hello guys, this is my first post here and hope you can help out since i know you guys are very smart. My problem is my cable speeds. I have cable and I installed it myself with one of those install it yourself kits, everything worked fine, download speeds were 400+ kb/s and when using a test site I would get 6+ mb/s. Now my problem is that one day I left to orlando and when I come back at the end of the week I find that my internet speeds are miserable. Downloading now is 80 kb/s max, and when i run a speed test and speakeasy i get download - 600 kb/s while uploading speeds are 90 kb, its ridiculouse. Ive been having this problem for about 2 months and cant take it anymore, I just hate waiting 1 hr for a 150 mb download. Hope you can help. Thanks

yea I did that and casually same day that they came, the internet started working perfectly, and after they left, it went all wrong again, dont know what to do...... any settings i can check to make sure?