(((Hugs))) the short nap phase is awful
. It will pass I promise. But I know it's not fun while you are there. 3-4 months is peak time for short naps so you aren't doing anything wrong, and LO certainly isn't doing it to spite you. DD was a complete catnapper at that age, almost permanently OT, but now she is a fun, lively, inquisitive 18 month old and certainly hasn't been harmed by it. Please don't feel guilty, you are doing LO no harm at all, it's just babies are hard work and they don't read the sleep books
Could you post a whole day in EAS format so I can see if there is anything obvious to tweak?
Do you shorten A times after short naps?
Do you know what personality he is? He sounds like he may have some spirited traits....
Can he sleep well in the car or pram? It really might be worth a day out (for your sake) just letting him sleep where and when he will, not worrying about the routine/nap lengths and just see what happens. Or if you'd prefer, a day at home just following cues and ignoring the clock. If he want a short A, let him have it and don't wake him. Sometimes a day or two like that can just help reset and get things into perspective x