Self soothing is a learned skill, that literally takes weeks. It's not something that will happen overnight, or within a few days. Your little one is just 4 months old, so dc's just starting the process.
I found that as dc matured, from 3 months to 4.5 months, dc ability to settle into sleep gradually improved. It took lots of patience and keeping calm on my part. Lots of patting-shushing, and staying near to support through the jolts.
Right now, you're just 2 weeks into it-- a week from now, it'll be better-- not completely better but you should notice somewhat of a difference. During the time, be as conscious of dc sleepy cues and making sure dc doesn't overtire/over stimulate prior to dc nap. You don't want to push dc awake time right now, just focus on helping dc to settle to sleep without the prop.
I hope the helps, I know it's not easy right now, but it will improve as dc matures each week.
