No offense meant of course, but I disagree to what Fergie F writes (if I understood everything correctly). First of all: find a teacher! Wrong techniques may cause damage to your body. As you already discovered a specific problem, it is dangerous to teach yourself.
The wrist should be OUT and pretty straight, so the elbow is kept to the front as far as relaxed posture permits. This implies wearing the bass rather high. Play with your FINGERTIPS, not the pads.
An excellent tutorial:
Your specific problem: If you play with your fingertips, the joints wil be kept bent INWARD, so they can hardly bend the other way. Fingertips are harder than fingerpads, so after growing some callus you will get the tone easily. Don't really squeeze the neck. Have the action of your bass checked by a teacher or a luthier. If necessary, use lighter strings.
No offence Chris and great points made i agree with if the bass is held high, but not so good if it is low. Since the side i offered is a general rule of thumb on the mechanics of joints, the variable are many in what a player seeks to do.
If the wrist is to far forward the mechanics do not work, regardless of height, yes the fingertips may curl and the string fretted, but the loading is still not stable, or as stable as it could be if the wrist is held back. It also brings in the elbow and so that means the shoulder has to be involved.
So with limited information about the OPs style it as about keeping the wrist straighter, the joints in line, and let the fingers apply the pressure correctly from the forearm not from the thumb.
Think in playing a piano......this is not a problem because the thumb is not involved in gripping, but playing and the wrists are straight and the natural curl of the hand and fingers used correctly.
It is the arms that control the height to the piano and because no thumb is using a gripping action ( this gripping is an un-intentional thing by the way) the pressures and strains are greatly reduced.
I can't remember many converations about piano heights, but those i do were all about setting the stool so the sholders are down (relaxed) and the forearms controled from the elbow, so the wrists hands and fingers have the best of movement afforded to them with the least of effort.
Bass playing should apply the same principals when ever they are afforded to it.
