Sleep HELP

My son is almost 11 months and he’s never been the best sleeper. He’s only ever slept through without a wake up once which is when we were sleep training him. He then was I’ll with tonsillitis which is when things went downhill as he wanted contact naps etc and now I can’t get him back out of it!! He is so hysterical at nap time and bed time and when he wakes through the night I really don’t know what to do. When I sleep trained before I left him for 5 mins and then went in to reassure him which seemed to work but it doesn’t work this time round! I’ve tried holding him which he then falls asleep but as soon as I put him down he’s hysterical again. The only way I manage to get any sleep myself (because I work full time) is to get him in bed with me which isn’t ideal. Please help I don’t know what else to do