Machan, Probably something wrong with your PC/network.
May be some malwares and unwanted programs suck your bandwidth. Firewall software ekak install karala (Zoneelam, Kaspersky Esmat wage one ekak) one wena programs walata witharak internet access permission denna (browser, torrent software, skype and other messengers wage) Thawaduratath prashanayak thiyanawa nam witharak 1MB ekakata maru wenna.