Am I being paranoid, or am I getting ripped off?

I've been running several ad campaigns with AMS. One of my ads (sponsored product keywords) has a $10 per day limit. Since March it's averaged between $2-$12 in clicks per day, and my ACoS has been around 29%. Last month, one day out of the blue I somehow ran up a bill for $30. I wrote asking about it, they told me they'd look into it, got back to me 2 weeks later asking for info I could no longer provide and I just let it go because things went back to normal.

This month it's happening again - 2 days ago I was charged $27, and today $21! My sales haven't changed at all (averaging btwn 2-7 books a day), but this is the first time I'm ever going into the red.

Amazon claims on my ad account that most of my sales are coming from their clicks, but there are 2 other sources I'm certain I get sales from. I'm beginning not to trust Amazon and I'm wondering if anyone else knows anything about what might be going on. I understand that my $10 a day gets spread out (if 1 day costs me $2, the next can be $18), but it almost seems like Amazon is making certain that happens now - when that wasn't the case in the past. It also doesn't make sense to me that the ads are costing me so much more, but my ACoS is remaining the same?

Just looking for some insight. Life has been good up to this point with Amazon, and I'm starting to get a little nervous.

32 views and no responses... I'm guessing everyone else's guess is as good as mine.

I dropped my daily budget last night to $7, and 9 hrs later I already supposedly accumulated $9 in clicks! I wrote to KDP 4 times now, and all I get is messages telling me they're looking into it. This is frustrating.

I'll quit complaining now. Needed to vent.