How do you tell your boyfriend not to come over? Easy. Talk to him. You're boyfriend and girlfriend, so I'm assuming you guys talk. Unless you live together, and then this conversation will get a little sticky.
Bob - instead of coming over on Friday night and staying throughout the weekend, would it be okay with you that you spend just Sunday with me? I've got some other things going on for Friday and Saturday and was wanting to get some other errands done as well. Great! Thanks!