Hello, welcome to the boards
I just wanted to add that my ds suffers from this too. The best advice I can give is to make sure he has enough fluids. My HV told me (and I think it makes a lot of sense) to treat his formula drinks as a meal, rather than a drink, even if he is eating solids. So he needs drinks as well.
If you can get him to drink water, then great, but I never could, so I dilute Heinz baby juice, half and half with water (it already says it's diluted as well), and he likes to drink this. He has a couple of bottles a day between meals (although, at your ds' age, he was only drinking the 125ml bottles 2x a day, and this worked fine).
If we don't do this, he has awful trouble. To get rid of the 'blockage' he has now, pureed prunes are always good (but not too much, or you'll have a serious nappy incident to deal with
).
HTH