userform duplicating add data

Guy's

Attached is a data entry form i've been working on as a project to help me learn VBA. I'm having a problem with it. I've got it to add the data from the userfrom (textboxes and comboboxes) to the next empty row on the worksheet. for some reason it's duplicating data that should be going into column a into column h. i thought it was because the cell in h has nothing in it but i've tried changing that by entering data. still nothing.

Can you have a look and see what my problem is.

thanks in advance