Family help, too much stress.

It isn't bad at all! Because at the end of the day you're the one who has the vision for your wedding. My bridesmaids used to ask me if I needed help but I really didn't because I knew what I wanted and it was better for me to do it myself.
Everyone will always have an opinion and be judgmental and try to push their ideas on you but at the end of the day you should go with what you want because you'll be happier knowing you did what you wanted anyway.

Stand your ground and tell them that while you appreciate their, um efforts, the decisions are ultimately up to you and FH.. other possible responses include that "you will take it into consideration", "thank you but we've already made a decision", direct no answers, etc. If they still don't get it, I'd just tell them thanks but FH and I have a grip on planning and don't need help with this. You could also try to find something with your wedding that you don't really care about and give them responsibility with that.

And no it is not bad to not want their help. Their "help" is not helpful if it makes you feel uncomfortable, pressured, annoyed, stressed. It's your day, don't let other people push you around, make the day yours.

Hey there! I’m sorry that you are feeling a little overwhelmed with your family.

You should not feel guilty at all for wanting to share all of your wedding planning with your family. They obviously love you very much and want the best for you, but you don't want to feel pressured into decisions that you don’t 100% want for your day! You can simply let them know that if and when you would like their help, you will let them know.

I completely understand your frustration. I would hold firm on not having all your cousins as the bridal party and do as you have been with just keeping your parents involved in the planning. Maybe also let your parents know to keep the plans within the small group and not inform the extended family.
If the extended family asks, I would just say I really appreciate your ideas, but we would like to keep some of the details a surprise.

The same exact thing has been happening to me. To the point it's causing physical stress. Don't feel guilty for not sharing. The less that are involved, the better. Just yes them to death

Let people know that this planning is a project for you and FI to take care of, establishing the planning, prioritizing of wants and needs, and budgeting skills you will use all your married life. And you want to work things through with each other, not with any committee of family. Unlike parents are paying for everything, which gives them some control of the reception, parents need not be involved in planning. And no matter how much they contribute, choices like the nature of the wedding, civil or religious,or formality, and general size, any vows, and the choosing if wedding attendants, are always, always, the B and G decisions to make. So is how the GM and BM dress. Thise choices are never the parents. So feel comfortable telling them you want all friends, or a mix of friends and family, and you will tell them after you have talked to the people involved. No suggestions need be considered.