Starting breastfeeding at 5months??

So I originally started breastfeeding my son as a newborn, but my health visitor knocked my confidence and made me feel like I wasn’t doing it right so I stopped and made the decision to formula feed. I’ve regretted my decision ever since. He has had cow and gate since I switched at 2/3 weeks old but now they’ve changed their formula slightly and he’s been very sicky and unsettled since. I was wondering if it was too late to restart breastfeeding? He’s 5 months old. I can still hand express a little milk, but it’s quite thick and sticky?