When a woman prepares for mikveh at home, all she needs to do at the mikveh before her immersion is wet her body and hair in a shower (the mikveh will have a shower available for that purpose), comb her hair again and check her body thoroughly for any barriers. There is no need to use soap or shampoo again even if you became sweaty since warm water will rinse that off.
We highly recommend that you use a checklist when doing your preparations. You should check off everything once on the list as you do your preparations. When visually inspecting your body for barriers, you should use this list as a guide to make sure you did not forget anything. Once you complete this list, you can be sure that your preparations are sufficient. At that point you should try your best to switch your focus from the preparations and immersion to thinking about your relationship with your husband and looking forward to spending the evening with him.
We hope that these suggestions help to ease your anxieties in your mikveh preparations. If you find that your anxiety does not subside, or that a specific point is particularly troubling to you, please get back to us.
B'hatzlacha!