mommy frustrations....

okay so here it goes....we finally "conquered" bedtime with nick and he starts getting up in the middle of the night like 3 and 4 times...i have a 2 month old that will sleep thru the night straight for more than 6-7 hours but my 3 year old wakes up every 2 hours or so calling out for me, crying mommy/daddy and/or coming into my room to put him back to bed....i finally resorted to buying a lock for the outside of his door tonight...i took him to home depot with me to pick it up and warned him if he didn't stay in bed tonight i would be putting the lock on his door for tomorrow night....i have been struggling with this concept for over a month....we went to the pediatrician for his 3 yr old check and she told us to lock him in his room to rectify his sleeping/nighttime issues...we just couldn't bring ourselves to do it...it just seemed soooo extreme, but i swear to god tonight i have just about had it....tonight after talking to him, warning him about the lock, reminding him about the reward toy we bought for him if he stays in bed for 5 nights - he still woke up at 1115ish and got out of bed crying hysterically for mommy or daddy....we were both downstairs - i was watching tv and mike was asleep on the couch...i called up we are right here go back to bed...he still cried hysterically for us - mike came up and went right to our bedroom and bypassed his room....i gave him 15 more minutes of crying and i came up and spoke very sternly and told him that he needed to get back into bed that he knew the rules and now mommy had to lock his door tomorrow cause he did not stay in bed....i closed his door and held it closed for like 90 seconds and he went wild - screaming and banging on the door but not as bad as i thought it would be or that i remembered from when i did it before....after the time passed - i went back in and told him in no uncertain terms that it was bedtime, that he needed to go to sleep and that we were not going to keep doing this...that tomorrow the lock was going to be put on his door until he could show me he can stay in his bed and go to sleep.....he kept trying to get me to talk to him, saying mommy mommy mommy to get my attention but i ignored him and continued my stern speech and then walked out the door leaving it open this time when i left...he moaned and whined a bit but fell asleep about 20-30 min later.....it is now 1230am and he is asleep, has been for about 35min or so...i checked on him and he is very sweaty, but sleeping in his bed...i hate that i have to put fear in him to do what i want but i have no idea what else to do....it honestly feels like we have tried everything...i have offered rewards, i have threatened punishment - so now i guess it is time to start punishing him by locking the door...hopefully it will pass and we can just put him to bed and he will stay there because he knows he should and needs to not because he is afraid of being locked in his room....
god please give me the strength to make it through this hell.....because i swear being a mother is the hardest thing i have ever had to do....