I went to Fashion School so my advice to you is that you accesorize real good instead!
go for a nice earring and necklace set , or wear a nice brooch, shoes and handbags that match always make an impressing touch! wear your slacks and nice blouse, just don't forget to accesorize!!!!
I'm Christian and we are having my daughter's Dedication on the 8th of Feb..I'm also a few pounds extra and most things don't fit..so I'm looking to add some dazzle to my wardrobe by accesorizing!
although here in Miami techinically its not really WINTER, but if its cold out, you can throw on a nice scarf or a hat
hope this helps and may your baptism turn out BLESSFULLY!