The poor love! What a rough ride.

If you've had to turn to special formula, have you investigated allergies? I'd be really cautious about introducing foods, if so. Is the vomiting actually affecting weight gains? Is that why the doc suggests solids? It's worth noting that the sorts of things you'd typically start with - rice cereal, purees - would have less calories and nutrition compared to milk.

They do grow so fast, don't they!? Glad you've got the reflux under control now at least