Well I am one of those Moms that did believe in establishing a routine for my two babies, and by remaining committed to it they did establish the habit by age 4 months of sleeping THROUGH the night for 12 hours and taking nice 2-4 hour naps during the day. I'm not writing this to make you feel bad, but just to offer a contrast to other Moms who have written who do not seem to think structure or routine are realistic. A mom who is firm, confident, and consistent does not need to have a baby that ALWAYS sleeps fitfully and wakes at all hours of the day or night. Normally; of course there are exceptions.
But on to you. You do need sleep. I hope you and your husband are taking turns with night time duties so you can get a few hours of uninterrupted sleep. I hope you have a friend or relative that will take the baby for a few hours so you can get a nap. If you want to give your baby the best care possible, you need to keep up your strength.
Part of the problem might be that you are always trying DIFFERENT things. I think babies are creatures of habit. The more regular and routine things are, the simpler their lives, the less they have to worry about. So my nap times were set in stone, my bed time was set in stone.
And I was not afraid of crying. "No baby ever died from crying," we said. Our rule was that we would let them cry for 45 minutes. Of course they did not usually cry this long. But if they did and I wound up getting them, I did not allow this to get me off my schedule or my routine. When the next sleep time rolled around, I followed the same rule.
Of course, you must be confident that your baby has eaten well, was burped and changed. I did not believe in the "snacking" approach to feeding, where they could have a sip or two whenever they wanted. If they snack they are never motivated to eat until they are full enough to last several hours. That's true of kids and adults, also! So whenever I fed him or her, I made sure he drank for a good 20 minutes on each side. If they fell asleep drinking, I woke them up. Basically, I followed the book "Babywise" to a T and it was wonderful.
But it's much easier if you start from day 1, and your baby is five months. I would say, make a decision and stick to it. I never rocked my baby to sleep because then they get used to it, it is their expectation, and you wlll always have to do that for hte next two years (or force them to change the habit YOU encouraged them in, and they don't like that!)! I put them in their crib and allowed them the opportunity to learn how to fall asleep in their crib. So if that's what you want to do, I would say commit to putting them down in their crib, let them cry it out and don't be discouraged if they don't accept it right away. My babies did not "cooperate" with my routine for the first three months but then, it was like a switch, all of a sudden they totally just started happily snuggling down when it was sleep time. I was glad I had persevered! Just try to be consistent each day and in a while things will improve (I can't predict when!)
take care, and I really and truly wish you well. I remember how stressful those days were.