ios 6 update

Hi there

I have iPhone 4G and I am using it for past 2 years without a trouble but I recently update my iPhone 4G to ios 5 and then ios 6. Thats when all **** break loose as the phone became very slow, screen start lagging, and watching a vidoe or listening to a song on cellular data became nightmare as the vidoe will stop halfway and will take forever to load. Now even checking mail is also hard.. Any help already tried resetting everything couple of time ( it's a weekly routine).