Gas Drops

My son is four weeks old as of the 19th and my husband and I have been giving him little remedies gas drops lately to help with what we think is gas. Since then for the last couple of days we have noticed he has had a increasingly worse amount of spit up. Every time we feed him he is very hard to burp and spits up what seems like a large amount, sometimes it's a small amount others it seems the amount he was fed or more. Today we changed his formula from Parents Choice Gentle to sensitive and from playtex ventflow bottles to Dr. Brown's. Since the switch and almost a day without gas drops he seems to be better. He has much less spit up and is a lot less fussy. My question is has anyone else experienced this with gas drops or similar symptoms? With our first we only used gripe water, this is the first time using gas drops.