Breastfeeding help

My son is almost 4 months old. I started off breastfeeding but after 6 weeks and going back to work I slowly started formula feeding. I'm almost exclusively formula feeding now so I'm pretty much.. well, dry.

I want to try to get my milk supply back and breastfeed again. Any tips on how to do this? I hate that I let myself get lazy and stop breastfeeding because it was "too hard". I'm upset with myself, I feel like breast is best and I want to get back to feeding my baby what I feel is best for him.

Pleaseeee any tips or advice is greatly appreciated. I've done a ton of Google searching but I'd just like some real life feedback !