I use 105 for e string .
One of problem is that for hammer on I push the neck to front and I don't know why so i can hammer on .
In this position I put pressure on thumb to move my bass a little front so I can do hammer on and I think thumb soreness is because of that too .
1) Get yourself a set with a 100 E string — easier on the hands; ‘nuff said.
2) "One of problem is that for hammer on I push the neck to front" — Okay, that’s a start. First you have to know where the problems are. Next, figure out a way to fix, or at least mitigate, each problem. Looking at it myself just now, I see I
can hammer on a bit without using my thumb on the back, but especially playing any string besides the G string, it takes a lot of tension on the forearm and hammering finger and the note doesn’t always sound clearly. In other words, hammering on does take a bit of pressure from the thumb. But, with lighter strings and lower action, it should take
less thumb pressure. Further, spend some time examining your hammer ons and learn to do them with the minimum thumb pressure necessary.
Another possibility to consider is avoidance. I have no idea how bad your thumb is, but a basic idea with pain is if some action hurts and is getting worse, don’t do it. Unless your bass playing is out front in the band and you are playing a signature line of a song that requires a hammer on(s), will the audience really know or care if you’re hammering on or not? Of course, hammering on is a basic technique that is used all over the place, but you may be able to at least reduce the amount of times you’re doing it, at least until your thumb gets better. Anyway, I know I’ve moved to lighter gauge strings and I avoid some things that I’d otherwise do because they strain my hand, wrist or forearm. Sucks, but that’s life.
Look for other situations where you’re using too much thumb pressure too and work on improving them too.
Warm up for a few minutes by playing gently, starting without the thumb and then gradually adding it, each time before you play. After you play, ice the sore area of the thumb for about 10 minutes (no more than 15 minutes or you’ll get frostbite and won’t be able to ice again until
that heals!). See a medical professional instead of listening to some dude like me on the internet
Just one warning about medical professionals: a doctor may give you a steroid (cortisone) injection which will make the pain go away temporarily (it’s like magic), but beware as that doesn’t actually solve the problem. It’s only to give it time to heal with rest and rehabilitation excercise. If you keep playing like normal (since the thumb won’t hurt any more), the original situation will only return in a few months, potentially worse. Then you could go back for another injection which again will work for a while (but a shorter time this time) and then when that stops working get another, and then another — but each time it’ll work for a shorter and shorter time until it finally doesn’t work at all and then that solution is over for the rest of your life and you’re back where you started or
worse. Worse, because repeated injections can actually kill the tendon tissue (necrosis)

Anyway, no need to get all worried about that - you haven’t even had a single injection yet! It’s just something to be aware of — some doctors, unbelievably, will just do a series of injections like that until the situation is beyond repair.