Hiya, my lo is 5.5mths & we had a lot of trouble with naps, he still puts on a great performance most naps. We found a lot came down to his temperment as well - he is stubborn (like his parents lol). The biggest thing which i know is hard is deciding a plan & being consistent with it. We fell into the trap of trying a certain way for a day or so then giving up, probably just as he was going to "give in". Tracy says start as you wish to continue, so bear in mind that using a paci or other props now might lead to prop issues later on (in saying that if all else fails & you both need sleep then do what you need to do for that nap). But it confuses them if one nap they get rocked to sleep/drowsy, the next fed, the next its paci.
We tried all the shh/pat & other "kinder" approaches, we found that he actually would cry up to 10min before falling asleep & that this is ok, its not CIO its them actually settling &/or protesting. We then had to do controlled crying to extend naps, as we were feeding every 2.5hrs because he would wake early & we were so scared of OT, so on suggestion of someone experienced in babies & based on what we had tried & what our lo was doing - we did controlled crying, so if he woke early we would leave him until he cried then let him cry then straight in to reassure him, then leave room, wait 10min, then go in & reassure then leave, we did this until he either went to sleep or it was 3hrs since he last ate. To be fair the 1st time was hard, I had a friend with me which helped. We soon found that for our lo, going in to him gave him a false idea that we would get him up & so he would scream/cry even harder when we left the room, so we pushed out the time of when we'd go in to him. eventually (which was only days) he slept longer, mainly as we were able to push out the times between feeds, he went from having 165mls every 2.5hrs to 220mls every 3hrs. so he was in a vicious cycle of snack feeding & catnapping.
anyway you may not have had time to read all of this, but I definitely know how you feel! we still have those days (after having them for 2.5mths).
Maybe post a days routine so that one of us might be able to see whats happening, also maybe post what you do when he either doesnt settle or wakes early.
lik pp you are doing a great job!!!!