i was given all the same 'advice' and told the same things, it made me wonder what i had done wrong to get such a 'bad' baby. but she was normal, just like yours is.
the meds took a week to 10 days to start to work, and she also had the mylanta till about 4.5months. so it could be so far that your ds hasnt received any relief. id give it another week or so and if you dont think it's helping take him back to discuss it as there are a fdew different types they can have and its really trial and error as to which works for your baby.
things that helped me were making sure she stayed upright for at least 20 mins after each feed, propping one end of the cot up, letting her sleep in the bouncer, swing or sling during the day as they are in a more upright position in these than in the cot or bassinette and lots of burping throughout feeds, it helped to get wind and any fluid up, so i knew she had had a decent feed without feeling like she'd brought it all back up afterwards as she brought little bits up and then continued to feed and she wasnt all full of wind and not taking as much milk as she needed due to wind.

you should be proud of the effort and commitment you have to this, i know its not easy, your doing great.
if bubs gets too much during the day, get hubby to take him for a walk or you go outside even just 15mins without the screaming can ease your tension and freshen you up to think strait