TT40 I can so relate. Especially when DD was younger we went through a few stages where every single night was at least an hour long drama and she wasn't even content to chat or play in bed but screamed blue murder even with me in the room with her. You are tired after a long day being focussed and active with your baby, baby is tired, you are allowed to loose grip a little... And you are definitely allowed to tag out! In fact you should do it more often if you need to. When DD was like that I would literally walk up to DH and say you need to deal with this, I can't handle anymore. Unfortunately DD at the time would only settle with mama which made it hard but at least if DH spent some time trying (fruitlessly) to calm her I could have the space needed to recollect my composure and calm down ready for round two hundred.

You are a good mother, a caring and responsive mother, otherwise you wouldn't be so worried about this. Get DH to tag team more even if Spock will only settle with you, it at least gives you a little breathing room and you can feel supported by your partner.