Bajan, sorry for the others getting off topic, but if you lagged out, there's nothing anyone can do about it. If you lagged out, technically you are at fault. If you had something good, I'm sorry for your loss.
what you mean is you have limited internet and 18gb is your limit till you get over charges your not saying that is your internet speed.
If anything you should try restarting your computer and/or router. If your internet speed keeps getting worse and worse you could have gotten a virus or maybe your router got ddosed. If the problem is your computer take it to the hospital (mac store/windows store). Yeah, and you probably can't get your items back unless you have proof at least.
I don't lag a lot, but I heard optifine always works I have it installed for zooming in on hackers (etc.) You should try it.