my little one is 7 months old and wont sleep through the night i have tried everything and i need some help.
Can you be more specific? How many times does your baby wake up? How’s daytime nap? How does he go to sleep? What have you tried?
she wakes up three times during the night, she takes two 30 min naps during the day. and i’ve tried the letting her cry and the pacifier and even a self-setelling thing i saw online, and none of them worked,
Hi! I’m sorry you little one isn’t sleeping well. You must be so tired. 
Has she never slept through the night? Or is this a recent thing? How do you usually put your little one to sleep?
Here are a few things that have worked for me, and I hope may help.
Try to have a pattern. A loose time and routine. That way the baby will know that it is usually bed time when … happens (like a bath before bed at night) or a lulluby before a nap. If you have a rough idea of when naps happen and what time bedtime is, it will help the baby’s body adjust to sleeping at those times. Also, try to have the exciting activities first and gradually go to calmer things as it gets closer to bedtime.
When putting the baby down to sleep, make sure he/she is still a little awake, but very sleepy. This helps them figure out that they can fall asleep on their own. So that when they wake up in the middle of the night, they can then fall asleep without assistance. Going to sleep is a learned skill for many babies. They need to figure out that they can do it without being held or rocked.
Also, most babies have a 30-45 minute cycle, where they will slightly awaken at that point. Once they learn that they can go back to sleep on their own, they can connect those cycles and take longer naps and sleep through the night. Sometimes soothing them before they fully awaken to get over the 40 min. “hump” (at nap time) can get them to sleep longer. (I think I read somewhere on this forum that someone tape recorded soothing messages to the baby and played it for him/her. He/she also recorded the message that he/she would sleep well all the way to morning. I haven’t tried it, but it worked for that person.)
If you can get your baby to take a longer nap during the day - 1 or 2 naps than are an hour and a half to two hours long - this may actually help your baby sleep better at night. Sometimes babies are so tired and over stimulated, that they can’t relax at night. Practicing falling asleep during the day will help a lot at night, too.
Some babies really like white noise. (The sound of a fan running or something like that.) It also helps to block out other noises during the day.
My main advise would be to work on naptimes. Be sure the baby is still slightly awake when you put baby down, and help him/her get over the 30 minute hump (preferably without touching him/her). Hopefully that would eventually work its way into nighttime. 
These are things that have helped me. I know all babies are individuals and have differing needs. And perhaps you have already tried these things. But I hope some of it might help your little one sleep better. 
My son did the same thing, but he thought when he woke up that he needed to eat. It was hard to break him.
We got this thing it was really neat made by The frist year. it was a two part piece one piece hooked on the side of the crib and the other part you put underneath the crib matress. When the baby cried or made a noise it would sound activate a vibration and sound u seleted to play. It also had a night light attatched for those midnight trips in the room. We got it at jc pennys. It really helped him because he would wake up and cry and it woudl sooth him back to sleep. after a whiel he didnt need it anymore.
Have u talked to your pediatrician. What does he/she recomend? They can usualy point u in a good direction. It seems like you have to find that one thing that works with each child. They are all different.