There are plenty of teams out there, it just depends on what competitive level you're on. There are competitive leagues in Calvert County that play during the week, double-headers, I think, between Monday and Thursday. They do have different brackets of competition depending on what bracket you get into.
There are also two leagues of a highly competitive nature in St. Mary's, one that plays on Tuesday/Thursday and the other on Friday/Saturday/Sunday. There are also numerous leagues in St. Mary's such as co-ed, fire/rescue and church leagues. I know St. Mary's has a tournament that is usually the second or third week in March that is before actual league play begins, so you could check with teams there. If you wanted to do something sooner, I think you'd have to check with some of the sponsor businesses and find out. Brass Rail Sports Bar in Great Mills is a good place to ask around. There's always someone in there who plays. And if you work on Pax, just ask, softball players are everywhere.