breastfeeding at 4 months and beyond.....how do I do it?

[elliott]

ds2 is nearly 17 weeks and exclusively breastfed. He's a very easy going baby who rarely cries and is a joy to care for....At the moment he has about 5 feeds during the day and one at night (I've just stopped waking him for a late feed) He is settled between feeds, which are approx 2-3 hourly depending on his demands and his sleep pattern on any one day. The fly in the ointment is weight gain - since he was 8 weeks he's gained an average of 2.5-3oz per week. I'm trying to ignore this, as he seems fine in every other way, but it does sow seeds of doubt about the adequacy of my milk when I see him drifting inexorably down the centiles (from nearly 90th at birth to well under 25th now!)
I would really like to keep bf going for most of the first year but I really doubt whether I can.
My current worries(!) are:

1. Should I do anything at all to try to increase his weight gain - should I try feeding every 2 hours whether or not he asks for it?
2. If I do decide more input is necessary than breastmilk, should I go for solids or formula at this stage? Clearly formula is better nutritionally, but my experience with ds1 suggests taht if I try mixed feeding, my milk supply is likely to decrease rapidly and we'll end up on bottles very quickly.
3. Introducing solids - my plan is to introduce solids when he starts to demand feeding more often, if things don't settle after a few days of increased feeding. When I do start solids, what's the best way to safeguard my milk supply whilst still ensuring that I'm meeting ds2's needs for more food?
4. Length of feeds - a full feed still takes 30 minutes - I'm waiting patiently for the 10 minute feeds promised in all the books - is this length of feed usual at this stage? He'll normally graze for some time on the first breast, and I generally take him off and offer the second which he will take enthusiastically for a short period and come off himself. It would obviously be nice to have shorter feeds but I feel wary of curtailing them too much while I know he's not gaining fantastically.

Anyway any advice/experience welcome. Sorry this is a bit long and rambling, I do have a bit of trouble pinning down exactly what I'm worried about

thanks tiktok. tbh ds2 seems fine, he's not exactly plump but he is as contented and smiley as can be I think that's why I get a bit confused - I think, well, I'm giving him breastfeeds when he seems to want them, and he doesn't seem frantically hungry, so why isn't he taking enough to grow on?
Actually my main reason for starting on solids was because I wanted to do it myself before he starts nursery in a few weeks time. Then I was just curious about his weight and was a bit shocked and disappointed that he hadn't gained anything.
I'm mainly concerned that I don't muck up my milk supply, but I think if I just make sure I feed before solids and keep off the formula I should be ok (unless ds2 decides otherwise of course!)
Thanks for helping me sort out what I want to do