7 week old taking too long to feed? (bottle fed)

[Gingerbreadpixie]

My 7 week old is formula fed and usually takes 5-6oz per feed, usually every 3 hours during the day and 3-5 hours at night. The trouble is, the feeds seem to be taking much longer than I suspect they should. Up to an hour. He starts off enthusiastically enough but tends to fall asleep, get restless and wriggly or lose interest halfway through. So I'll change his nappy or put him down in his crib (after burping) and within 10 mins he's crying again. So I'll offer the bottle again and he'll take it then lose interest again and I'll put him down and he'll start crying again etc etc. By the time he seems satisfied enough an hour has passed! Then by the time I've settled him it's usually only 90 mins till the next feed is due. Is this normal? Is it time to switch from slow flow to medium teats perhaps?

Possibly a slightly stupid question ... But what happens if he doesn't finish the bottle? Is he definitely hungry for the whole bottle?

Also, if he takes ages to finish a bottle, is he definitely hungry just an hour a half later? Are you feeding to a "routine" or to baby's cues?

We're feeding to baby's cues. ie, when he starts sucking mine or his dad's arms/shoulders/chests etc!

If he doesn't finish a bottle he'll either sleep, in which case ill leave him, or he'll start fussing and fist-sucking ten minutes later. In which case ill offer the rest if the bottle. It's this that causes the to-ing and Fro-ing.

yes I would try a faster teat

I've got some vari flow teats and some medium. Should I try vari flow first out of the two?

are the age guides on the packet the same? Mine never got on with variflo teats so I used medium flow instead