My 2 1/2 month old baby use to sleep 5 hours through the night, now she won't let me put her down, every time I rock her to sleep then try to put her down she wakes up and crys so then I pick up and she will go back to sleep within a minute, then I try to put her down again she will wake up this happen several times through the night. Please help

You are going to have to put her down and let her cry. Do not pick her up, she is getting used to your attention and it will not help if you want her to sleep through the night. I know it is hard to do, but better in the long run for both you and baby.

I wouldn't even rock her to sleep. Just put her down, give her a kiss, and tell her good night. Be consistent in your routine.

Do you swaddle her?

Babies love the smell and touch of their mother, and other close family members. They also love to be held close. It makes them feel secure. Your baby like most other babies, is manipulating without trying to. Your baby is used to you holding it and therefore is not wanting to let that go. It doesn't hurt the baby at all to cry. It might take a few days, but in the long run it will work out fine. Just don't give in, unless it's feeding time, or cuddle/play time. When it's bedtime, then he/she can cry itself to sleep. Just grin and bear it, because it will help out a lot... trust me. :)

Yes, swaddling is a good idea, it makes them feel secure.

Or you can just give in and let her sleep with you. It took me weeks to get my kids to stay asleep at this stage. As soon as I put them down, they would scream. I tried all the different suggestions. Eventually, they got used to sleeping alone. But in retrospect, it might have been easier and more natural to let them sleep with me. I know this is not what Americans do, but... it IS an alternative.

Other animals don't put their babies far away from them, and in many countries it would be considered odd. Just an alternative.

Or you can just give in and let her sleep with you. It took me weeks to get my kids to stay asleep at this stage. As soon as I put them down, they would scream. I tried all the different suggestions. Eventually, they got used to sleeping alone. But in retrospect, it might have been easier and more natural to let them sleep with me. I know this is not what Americans do, but... it IS an alternative.

Other animals don't put their babies far away from them, and in many countries it would be considered odd. Just an alternative.

This is great advice. The advice I gave is what everyone told me to do, but I didn't, I let my baby sleep with me. He eventually got to where he wanted his own bed, and still now and then he comes and crawls in bed with me. It's no inconvenience, never was, and it kept him happy, and me content to have him close, and know he was safe.
However for many women, this isn't an option, as it's too difficult to sleep good enough to feel refreshed come morning.

If you are going to swaddle her, remember to have a fan going in the room.

Recently there was a study that said Sudden Infant Death syndrome was dramatically reduced if there was a fan in the room. The couldn't explain why and would study further.

However, I think the deaths are in part because the baby's internal thermometer is still developing; and if they start to overheat and there is no circulating air they can't get rid of that heat and their little body starts shutting down in order to cool itself.

Also you should educate yourself on swaddling, there are some who believe there are risks:

Swaddling - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Swaddling_clothes)

Or you can just give in and let her sleep with you. It took me weeks to get my kids to stay asleep at this stage. As soon as I put them down, they would scream. I tried all the different suggestions. Eventually, they got used to sleeping alone. But in retrospect, it might have been easier and more natural to let them sleep with me. I know this is not what Americans do, but... it IS an alternative.

Other animals don't put their babies far away from them, and in many countries it would be considered odd. Just an alternative.

I'm not sure I agree, some baby's die from asphixation because the mother accidentally smothers them while asleep; or they die because a pillow or a heavier blanket or comforter goes on top of them, or they end up face down in a pillow an a blanket and can't breath.

Young children until they are strong enough to move such items or themselves should not sleep with parents in my opinion. It's OK provided the parent stays awake; but if the parent should fall asleep the child is at risk.