I'm looking for opinions and suggestion on what I'm doing with my DS during the day.

My DS is 3 months old and does not settle well for his day time sleeps. I have tried a couple of different methods. I have tried putting him down once he has fallen asleep on me, he generally wakes in less than 10 mins. He gets longer streches of sleep if I put him on his side or his stomach, but concerned about SIDS risk, (DH is a smoker so that is 1 extra risk factor). I have done the put down awake, pat untill asleep, patting each time he moved untill he was fully asleep, again he settled quicker if on tummy or side. His sleep cycle is about 40 mins. He will only do this for me once a day, after that he just cries if I try this method. I generally wrap him If I am going to try to put him down (as per SIDS guideline) if I put him on his tummy his arms are free. He doesn't like his arms being restricted, when I have done this he wiggles and cries till he has them free, so I wrap him and tuck his hand into "pockets" that I have made in the wrap.

The best method for day time sleeps are to put him in his baby carrier/sling and to continue whatever it is I'm doing. Once he is settled I can sit down and relax, but if I sit before he has settles he will start to cry again.

At night we generally don't have a problem. I put him down awake at 8.30pm, he self settles, will wake anywhere from 3-5 hrs later (3 more often than not), gets BF then back down. As the night progresses he gets harder to settle, so by 4 pm he need to be cuddled and patted for an hour before I can put him down, but he will be awake an hour later. Then he needs to be pretty much strapped to me if he is to sleep.

So my question is, is what I'm doing considered a reasonable method for day sleeps or am I setting myself up for trouble ahead?
I am concerned about him getting too big to carry, I have had a couple of headaches from the weight of the carrier on my shoulders.