Contrary to what Betty suggests, I wouldn't suggest weaning knackered, unless like her you've been specifically advised to do so by a paediatrician. There's a reason why NHS guidelines say hold off introducing solids until 6 months. I also found that solids made absolutely no difference whatsoever to how well my DD slept (I started her on solids at 6 months, per the guidelines).
Roller this is roughly the trajectory of getting past DD's crappy 4mo sleep regression.
At about 5 mo, I started helping her learn to self-settle to sleep at night. This involved stopping feeding her to sleep (kept lights on for bedtime feed, didn't zip her into sleeping bag until after feed, read story between fed and putting down awake) and doing a version of sshh-pat to help her settle. The first night it took something like 90 minutes of me sshh-patting. She was never full-out crying, more just mantra-crying/ shouting or just chuntering away to herself. I'd ssh-pat if she was getting worked up, then would hide out of sight under her crib, and repeat. We made good progress for about 3 or 4 nights, then she majorly protested for a few nights (hysterical crying as soon as I put her down), so I just fed her to sleep on those two nights and started again. Within about 10 days (from first starting) I could put her down awake and leave the room and she'd fall asleep. At some point during those 10 days I moved from hiding under her crib between ssh-pats to leaving the room and standing by the door, going back in if I needed to help her settle, until it got to the point that I didn't need to go back in. There have been several blips of varying degrees in the 3 or so months since then, but now she consistently falls asleep on her own within about 10 minutes. Some of the blips have been pretty major (e.g. her being ill and unable to sleep other than propped up on my chest all night), but we've so far always managed to go back to self-settling quite quickly (it might take a few nights of me having to do a bit of tummy-rubbing as she falls asleep, or sitting by her cot, or popping back in a few times to help her settle).
Self-settling didn't immediately help her night-wakings though. What helped that was moving her to her own room (at 5.5. months - made a difference straight away, as I think we were disturbing her in the night) and me setting limits on when I would feed her (at about 6 months) and at other wake-ups sending DH in to settle her instead (which he'll do by picking her up and rocking her - we've never had any luck resettling her in her cot if she wakes up in the night, she either needs to be fed or picked up and rocked back to sleep). Now, at nearly 8 mo, she goes down at 7ish, feeds once in the night, and I have to wake her up between 7 & 7.30 in the morning. I'm sure it'll all go tits up soon - the one thing I've learned over the last 8 months is that her sleep progress is not a linear progression.
I have to say that I had a strong 'instinct', when I started the process, that she was ready to start self-settling. Likewise, I had a similar instinct that she could get by on fewer night feeds when I started limiting those at 6 mo. I'm now pretty sure she could be night-weaned entirely, but I can't be bothered to tackle that until after Christmas as doing one feed in the night isn't an issue for me at the moment. So, listen to your instincts on what you think will help the sleep situation, rather than what you 'think' you should be doing, or peer pressure.
Sorry for epic post - hope this is helpful.