Is it legal for the prosecutor to dismiss charges and then file them again a few months later?

My ex-wife turned me in saying I was harassing her. The cops showed up at my home along with my probation officer to discuss it with me and searched my home. It was right after deer season and my 14 and 16 year old had been out here deer hunting. While searching my 16 year old's room, they found 5 of his deer rifles. They took the guns and asked if I would come up and do a UA I said yes. They left allowing me to drive myself up there. I passed my UA walked out of the jail talked to my probation officer. She thought it was absurd. She leaves and a detective comes out and wants to talk to me. I go in and next thing you know they issue a search warrant to go back to my home and search only my son’s room again. They found 4 more deer rifles. I didn’t know my kids had all their rifles at my house. Anyway they charge me with 4 counts of unlawful possession of a firearm set my bond at $100,000 10% surety, hold me for 9 days then walk in and dismiss all the charges. This was mid-December. The first part of February, me and my 16 year old was driving in town and seen my ex-wife and her boyfriend. My son does not like the boyfriend. My son jumps out of the truck going towards the vehicle they were in, yelling at the boyfriend. I stop my truck, then get out to try and get my son back in the truck. My ex-wife calls the police. I get arrested again and they brought back the gun charges. The prosecutor called my son to check our stories, which were the same. I spent 4 days in jail before my girlfriend got me out on a $50,000 10% surety bond. I need help. She has called in bogus incidences before and the police are aware of this. She has let my son quit school without even discussing it with me and he wants to live with me. I take UA's on a regular basis and am doing well other than this.