People tell me to let my 3 week old baby cry it out?

Im a first time mum n my lil girl is 3 weeks old and she normally quite good of a nite sleepin but recently she has started to cry now and then after a couple of mins after puttin her in her crib. Shes fed and changed and i give her a lil cuddle and she starts driftin off i put her down bt she starts crying which i then pick her up and she calms down and sleeps They only way she sleeps without cryin is in mine n my partners arms or chest. Which i say to my partner that she must like cos she can feel warmth and my heartbeat as thats what shes heard inside the womb. People keep sayin to let her cry herself to sleep bt i have read that you are not ment to at a young age as they need comfort? Is this true? I tried lettin her cryin it out once bt she goes for ages anf i hate seein her so distressed. I just dnt find time durin the day to do house chores or even make myself something to eat as shes always unsettled and needs me and have to wait for my partner to get home. But is it true not to let her cry it out and what can i do to make things easier? Thanks for any advice