Big hugs! Keep hanging in there, I promise you will see the light.
As you know the real resolution is getting your LO self soothing. If shush pat isn't working, then at 19 weeks you can consider PU/PD.
As someone who has recently trained (still progressing nicely) my 19 week old, I'm going to write a few things which really helped me.
1) white noise, it is a form of prop but it gets her to relax (she is also very spirited so I was going light headed from sushing 😂)
2) wind down, before a big nap I have around 20mins minimum of quiet time, with no toys, some lullabys and some cuddle but also quiet kick time
3) there will be tears but the more consistent you are, the fewer tears they will be. My LO gets loudest just before she falls asleep. It's almost comical, she'll go from a ridiculously loud wail one second to sleeping the next (almost like one last big complaint and effort to get me to give in)
4) allow time for your LO to fall asleep. If you put them in the crib 5 minutes before they are due to sleep and they take 20minutes to sleep, your LO may be overtired and the whole process may be harder and impact the rest of the day. With your wind down, that's about 40 mins
5) at first I cheated a bit and focused on the two main sleeps, big afternoon one and night time. The other naps were in the sling (if the pram is working for you then I recommend that). That way you are removing feeding to sleep, it is no longer an option but your LO and you are not too tired. Once you have your confidence up after a few days, then do all 4 sleeps. If you want quicker results, then maybe go for all 4 straight away. It will be harder but results will be quicker!
I ended up hurting my back with PU/PD, so I went to see a sleep consultant. She recommended an approach called hands on. You wind baby down, do bed time routine, put on white noise and put her in crib. Once she's in the crib you don't pick her up for 20 minutes. You can sing, talk to, stroke, caress and pat (anything to comfort but not picking them up). If at 20mins your LO isn't asleep then pick her up and get them to sleep any way you can. It only took 8 minutes for my LO to sleep ( I was staggered, it was noisy but quick). The longest it has taken is 19 minutes. Now she blows raspberries to sleep and I get the occasional moan on complaint.
Good luck! Try and stay positive, I know how hard it can be.