Wont start after 3 days of sluggish starting(like bad batt)

[/b] I have a 1993 ford aerostar van, 130k miles. Runs good. But a few days ago wouldnt crank, before thant 3 days before cranking was sluggish, like a weak battery.I thought was due to sudden cold weather. Cleaned battery post, got corrossion off. Was given a jump 3 times. Still goes click auto parts store checked batt with a load, said batts okay.I notice batt terminal can be moved(slides0 yet is tight. Solonoid on wall kicks in good. So with the 3 days of sluggishness, thought was batt(corrosion loose terminals0. But everyonessays is starter. Any clues, thanks ken in myrtle beach. Mar 2nd