I don't have adhd unit I do find it hard to concentrate. I find a vape in the evening let's me watch a film/programme without fidgeting or picking up my tablet.

Sounds like you’re making the same mistake I did. When sending money from my wallet to vendor, I was typing in the amount of dollars, rather than the amount of Bitcoin. If you type the Bitcoin amount in, that amount won’t change so you’ll always pay the right amount.

I second this, I always send by the btc value, it may be a weird looking number but its easier to match up and isn't going to change. I'm going to assume you're using an exchange to make the payment.

I'd really encourage downloading an easy to use wallet like electrum, much safer than say coinbase. This also lets you choose how fast you want the bitcoin to arrive :)