Hi Vaintx
Welcome to the boards! Good to have you here.
First up - defo get Tracy's books - they will come in very handy. I found BW Solves All Your Problems especially helpful.
Second - you can find some sample routines for your age group here
http://babywhispererforums.com/index.php?topic=164253.0There is info here about making the transition from 3hr to 4hr EASY
http://babywhispererforums.com/index.php?topic=63161.0And here as well -
http://babywhispererforums.com/index.php?topic=120362.0You mention you give him medicine - what is this for? the reason I ask is that some medications can effect the advice that people give you...
And have you developed a wind down/sleep ritual? You can find more info here
http://babywhispererforums.com/index.php?topic=64277.0At first glance there are a few things about your routine that jump out. At this age the average awake time is 1 hr 45min to 2 hrs and day sleeps are around 2.5hr to 3 hrs consisting of 2 naps and/or a catnap. Also generally you should be aiming for a 12 hour day so if LO wakes up at 7am you should try to get him down for bed by 7pm.
Remember when making changes to your routine to go slow, increase A times in increments over a few days and allow at least 3 days (or even a week) to see any developments.
You've got a lot to take in here so I'll let you read and digest and have a think...get back if you need more guidance there are lots of lovely helpful parents here so don't hesitate x