I think there are very few people lucky enough to know exactly what they want to do in life. Most of us, from a succession of jobs, learn what we NEVER want to do again, which gives some inspiration to find the next thing. You are simply normal.
Even when life is working perfectly, being a mom is an incredibly demanding yet BORING job. I was so lonely those first few years when I stayed home with my daughter, but when the 2nd arrived I had a network of moms in place for play dates and outings without kids.
It sounds to me like you are down now, but you could even be slightly depressed. Have you talked with your doctor about this? Be open and really tell her what you feel. I had post partum depression when my 1st child was 3 months and I felt that "all I have to do is take care of this little baby, why can't I do that without feeling tired and crying all the time". I got help and felt better within weeks. You should also let your husband read the above, or just email it to him with the header: "something I have been keeping inside and don't know how to talk about."
If you want to be more creative in play time with your son, just mimic what the school does. Have some blocks for building time, then make a mess with cooking pancakes together (he can break eggs and stir), then read to him for a while, then tell him it is time for quiet play or a nap, etc. Or just take him places you like: when mine were little I would strap them in the stroller with a lunch snack in front of them in a divided container (some cereal pieces, some rolled up ham, some strawberries) and a sippie cup and take a long walk in a busy town to window shop. It takes pre-planning to go anywhere with a kid, but at this point they still just come along because they have to. Plan driving time around nap time. Mine are 10 and 13 and now don't want to do half the things I enjoy, but now they can entertain themselves, so there are positives with every age.
Is the orphanage still a dream? Is the artistic end of things still fun? How about a part time job in an art supply store? Weekend hours when hubbie can do child care? Or volunteer at a local orphanage or adoption agency, perhaps you can bring your son? Or just volunteer for the local anything, call town hall and see what groups are in your town (our town has a website with listings) that need a helping hand. There are ladies who maintain the flower planters at various places on town, and a child can easily sit in the stroller while you help and chat with them. ANYTHING that brings you in contact with other adults will bring some social activities or even friendship into your life.
If one child seems too much already maybe this is not a good idea, but once we had 2 girls they seemed to keep each other entertained a lot (of course not the first baby year, but after that). And the big sister was a lot of help to me and learned some good sharing lessons. Of course you could have 2 kids that fight all the time, but who knows, maybe when the need arises you would become a great disciplinarian and find your "fit".
I have a degree in Physics from a Ga. Tech and worked in the super technical world for many years before I finally realized I like the marketing/sales aspects much better. I "moved" my career in that direction. In hind sight I can explain why I made the progression of job moves, but at the time there was often the "I have to get out of here" motivation that made me find another job. I guess I have been a good bull**** artist, but in looking back it actually all makes sense (I am 49). I too had no clue what I wanted to do with life, but there have been distinct stages and I am in the next stage now (working part time again after staying home for 10 years).
I would say take a small step now and call about 1 thing you might enjoy - is there a book club, walking group, library reading hour where other moms of toddler congregate, etc. Set up 1 thing to look forward to, and then next week plan 2 things. The momentum might build from that, or you might find some things are not as fun as you hoped, but at least you got out of the house and did something.
You are not a loser or a failure. You are actually quit thoughtful and caring to even think that way. A true loser would just sit and veg out and not even think what is best for the future or for their child.
Consider yourself hugged.
Catharina