You're not useless at all - look how hard you're working at this and how far you've already come! I completely agree with the others - you are both learning right now. This always entails a bit of trial and error.

In the second month of life babies are more unsettled and cry more. They just do. Sometimes there are other thigns going on - as you've identified, tiredness & overstimulation, or reflux etc. For the most part this is all quite normal.

Don't get me wrong, it's hard right now I know, but it will get better. Sometimes all you can do is just ride out the tough times by doing whatever makes things easier for the both of you. If she likes the sling, then use it as much as possible. Do you co-sleep at all? That can be a lifesaver and makes feeding easier too if you can get the hang of feeding lying down. Take whatever help you can from others. Even having someone watch her for a few hours while you catch up on sleep. Get others to do the shopping so you can stay home and let her rest more - a few quiet days can make big difference sometimes.

These can just be temporary solutions till things settle - then yiou can go back to putting her down for sleeps and using a pram etc. Sometimes, especially as new mothers, we worry too much about what we should or shouldn't be doing - according to recieved wisdomm or the so-called experts - that we actually end up making life so much harder for ourselves. Even if she was happy sleeping in a cot earlier, that doesn't mean she can do it right now. But equally, if you take her into your bed now (for eg) it doesn't mean she won't be happy in her cot in a few weeks time.