Don't worry it's not too late to be able to build up your milk supply as you have only stopped feeding very recently. As you know, breastmilk is best for your baby so if you can continue to feed him breastmilk whether it's from breastfeeding or expressed breast milk, that really is the best start for your little one. It sounds like this is what you want anyway good on you. If i was you, I would seek the help from a child health nurse who is also a lactation consultant.... or just a lactation consultant, however they do charge for their time so depending on what you can afford too. They will be able to help get you back on track with the breastfeeds and show you ways how to get your little one interested in it again.

Your little boy is taking a liking to the bottle because the teat allows the milk to flow much faster than a nipple does, hence he doesn't have to work as hard to get any milk out, as he would if he was on the breast/nipple.

Keep offering him breastfeeds and express regularly with a reliable pump and this will help increase your milk supply again. Offer him breast first then the bottle if he still seems unhappy after that.

As for what prescription drugs are safe for when BF, definitely see an LC about that or your GP as they will be able to give you all the info you need