totally not alone... i felt like that for months... probably about 8 months, then things improved, but also my mindset improved too....
its the hardest time of your life and anyone who says otherwise, well i wouldn't pay them any attention...
i just wanted to say that the babies you are comparing yours to, those babies will have their turn of being holy terrors, trust me.... in my mothers group my baby was the only one who didn't sleep well, but over the last 3 years i promise you they have all had their share of hellish phases, its just that my dd went through it early.... just because they are settled for a few weeks doesn't mean it is going to stay that way, they are so unpredictable, you just have to take each day as it comes, and when its a nightmare day or night, just repeat that it will not last forever....

although at the time it feels never ending, and the exhaustion is all consuming, it honestly gets better and when you are on the other side you realise how quickly things passed... just try to get as much rest as possible and go with the flow, let your baby lead, and try to enjoy the good moments and not tense up every time she cries... sometimes things get worse before they get better, and there isn't much you can often do but wait it out.... but i promise you it gets easier, and the exhaustion also gets easier to handle, your body adapts...

good luck, don't compare babies i promise you they all have their moments... you might find in a few months she is sleeping through and is an angel, and the other people you know are going through a hard time, everyone gets their challenging moments i promise.

take care of yourself and don't be too hard on yourself, its still such early days, in all honestly for me the first six months took a lot of adjustment.