1992 Pontiac Bonneville Replaced starter, car still won't c

Engine Mechanical problem
1992 Pontiac Bonneville 6 cyl Front Wheel Drive Automatic

Our car wouldn't crank about 2 weeks ago, the battery was completely dead- we replaced the battery, then about a week later, (All connections have been checked and thoroughly cleaned) it did the same thing, it wouldn't crank (or turn over) the starter had been dragging a bit for a while, so we replaced the starter- we had no problems for about 3 days, then it did the same thing- would not crank (or turn over). I replaced the starter again, because the head looked a little different on the one replaced, however, I could not find a starter that looked identical to the one I took off- my car has tune port injection- I was told this starter should work- I put on a brand new starter- it cranked, and then immediately would not crank again- all it does is click. What can it be? Do you think it is the neutral safety switch? Where is that located and how can I test it?