If you're typically only doing 9-15 reps of OHP per week, then it is very likely that you're stalling due to insufficient volume. You're doing a bodybuilding-style split, which depend on being able to generate enough fatigue in each session that the muscles trained in that session will take the rest of the week to recover, and actually being sensitive enough to intense training that this week-long recovery is productive (i.e. resulting in muscle growth) rather than a waste of time. These two things seem to largely depend being genetically predisposed to gaining muscle from intense and infrequent workouts, and/or being on steroids. If that's not you, then you may be better off with a program that works each muscle multiple times per week.
Here are some examples of 4 day/week programs that would allow you a higher frequency of overhead pressing, meaning you can still do 3x5s, but you'll be doing them more often. These are all based around strength training exercises (compound movements, not that much variety) rather than bodybuilding (huge variety, many exercises targeting the same or overlapping muscle groups). The exercises are just examples, you can alter as you see fit. If you prefer bodybuilding-style exercises, just substitute those in while following the theme of the split/program.
Push/pull 2 day split (repeat twice/week):
- Day 1 (push): Squat, bench press, overhead press (each session, choose one of bench or OHP to go first, as the main pressing exercise for that session)
- Day 2 (pull): Deadlift, chin-ups, core work
Upper/lower split (repeat twice/week):
- Day 1 (lower body): Squat, deadlift
- Day 2 (upper body): Bench press, chin-ups, overhead press, core work
Whole body 4 day program:
- Day 1: Squat, bench press
- Day 2: Deadlift, overhead press, core work
- Day 3: Squat, bench press
- Day 4: Chin-ups, overhead press, core work
Or if you really want to keep your 4 day body part split, you can try increasing the volume by switching to 5x5s for OHP. If you need to do fewer reps to increase the weight, then do increasing numbers of sets and reps at the higher weight, then go back to 5s at a lower weight. E.g. Maybe one week do 140lbs 2x3 reps, 2x2 reps, then drop the weight to 135lbs and follow with 3x5 reps. Then the next workout, try to go for 3x4 + 1x3 at 140lbs, followed by 2x5 at 135.
Another strategy that may help is to buy some fractional (AKA "change") plates, which will allow you to increase the weight in as little as 1lb increments.
