The pains you describe... are they two separate pains?
The one which you say feels like you have been kicked between legs could be SPD (pelvic girdle pain) that can feel very much like that and moving, especially if you are parting the knees or twisting does feel like that, I have it and it feels like someone has stuck a knife there! I have seen the ante-natal physio (via midwife referral) for mine (am now 37 weeks) and have been advised what to avoid so as not to aggravate it, and what exercise to do to improve it - get your midwife to advise you what painkillers you can safely take.
The one you say is a constant stomach ache low down, assuming that feels like it is in your muscles not your gut could be any number of things really, so wouldn't like to say if you should worry or not. If it is first baby it could well be the muscles being stretched which is perfectly normal - just so you know you don't necessarily need to worry - however, it could be something else.
If you are concerned (obviously you are!) you could go to the ante-natal unit at your nearest hospital and ask to be checked rather than wait for your next midwife appointment - take your notes, but you don't need an appointment. I did this at about your stage of pregnancy as I had had food poisoning and then didn't feel baby move for few days so was convinced it had died, was stood in reception in tears. They were totally fine with me, checked baby and all was fine - worth it for peace of mind.
They could check heartbeat and also you for what is causing the ache.
The not knowing is the worst, so ask for help from the experts, get suitable pain relief and ask your OH to keep his frustration to himself as it won't help you keep calm.
Good luck, I hope everything is fine, I am sure it is better than you fear, there are many innocent explanations but get the real experts to examine you for proper answers.
Fear is horrible, so go easy on yourself.