My 98 Dodge interpid 3.5 V6?

So I travel from Bellingham to Everett area atleast 2 to 3 times a month. As leaving Everett this trip I did my usual flluid check before heading out. I then grabbed some anti freeze and added about just above half into what I thought was resevore or overflow but found out today it was actual raditor. Car did fine back home and once in town did 4 back and forth trips to parents about 8 blocks to and from. Then another trip out to Lynden in county about 15miles there and back. When heading home went outside and it had since snowed about 4inches. Got butt home in bellingham still no problems. Wasnt til I once parked car at home that night and left it for almost 3 days with out driving did the issue start. Started up car waiting for it to warm up but it wasnt getting any heat, with wheather so cold I just took off in hopes heater would kick in, then looking at my temp I noticed it was above where it ususally sits and was sllowly moving on up to the H. Pulled into gas station waited a few to cool and proceeded with adding rest of antifreeze and started up to add a jug of water also. Turned back for home and driving back it only took about 4 min if that for it to reach the H tempature again got home few sec and parked. Can you please help me, this is my only running vehicle need to have transportation asap, Thank you so much for your time