Do I Keep Going?

I'm in two minds if I should keep on going with breast feeding or start introducing formula. I've successfully got through the last 4 months feeding Joel soley with breast milk but after I had him weighed on Tuesday - 14lb 15oz which according to the health visitor and the red book chart it's a bit of a dip. The last time I had him weighed he was a few days into 3 months and weighed 14lb 5oz so it is only 10oz he's put on. 

As he hit 4 months he has become more unsettled during the night and waking every 2-3 hours but not feeding for very long. I  found in the day he would feed for short periods and stop, sometimes just looking around or he looks at me and smiles which is sweet but I'm so unsure if he is getting enough milk. He seems quite happy to suck on a dummy. 
I have been thinking of stopping breast feeding for the last few weeks as at times I just feel I want me back especially the 2 hourly feeds becomes exhausting, so it would be great if someone else could do it. Something stops me from taking the plunge though, maybe because I'm thinking I will not have anymore babies so I should treasure the moments of bonding. I really don't know what to do for the best.

I can keep going and see if his weight creeps up or I just gradually introduce formula then naturally my milk should disappear - oh the dilemma.

Pros:
Best for baby
Always available
No cost
No preparation

Con's:
May fill baby up more
Mum will be free 
No more worries of feeding in public

Has anyone else had these thoughts?

I NEED SLEEP

This little bundle of joy called Joel is not letting me sleep, I thought growth spurts only last a day or two but I'm sure this one is on a permanent growth spurt with regular feeds every 1 - 2 hours if I'm lucky it can go to 2 - 3 hours but even so he doesn't like to be put down some days he can last about 30 minutes in his moses basket or chair before waking and screaming to be picked up but some days it's 5 minutes, it's exhausting.

I have started to crave being alone as I need a break from it. If its not Joel demanding feeds or to be held its Ollie needing my attention. I knew it would be hard having two little ones close together but on top of dividing myself between the two I'm just not getting enough sleep so I'm irritable, moody, emotional, stressed and my patience has gone out the window but I'm surprising myself how I'm carrying on with just about 3 hours sleep some nights and that is often broken sleep.

The joys of being a parent :)