1998 ISUZU Hombre speedometer problem

I have a very strange problem with my 1998 ISUZU hombre pickup truck. It started out just speedometer fluctuating. When I was doing 40 it would fluctuate between 60 and 100 miles an hour.
Then not only is the speedometer fluctuating but the battery light on the dash (Slightly) started to flash temporarily off and on.
As if that was not enough, now the speedometer fluctuates, the battery light flashes off and on randomly, and now the alternator is acting funny, it drops from its normal 14 -15 Volt position on the gauge to zero and the car seems to miss at that point. The alternator quickly recovers and everything is back to normal for couple minutes, and then it starts all over again.
I have not a clue, and have checked the post on Google and search the Internet. I've not seen anyone else with this type of problem. Is anyone that familiar with the Hombres(S-10, Jimmy) who might know how all these three are related. Well, the battery light and the alternator are obviously related, but the speedometer fluctuating throws me. This all happened over the course of the week and seems to be getting worse. At this point I don't know if I drive it whether I'll be able to get it home without a tow truck.
I need some help on this one.
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