I am so sorry to hear about your past experience!
Take your DP and ask to speak to the head of midwives at your hospital tell them your concerns. Because of your PTSD you will be at risk of ante natal depressions and post natal depression so they will need to know this.
You need to be clear about your treatment, you can request always having your DP in the room, you can request no internal exams (remember they are done for a reason) or ask to only have female doctors, midwives treat you. The only problem with this is that in an emergency you may not have an option as it depends on who is on shift and seniority etc. This can all be stated on your notes, women can request certain care for lots of reasons including stress or religious beliefs
Your midwives will be able to advise you further but if you don't feel comfortable with them you can find someone you do feel comfortable with and raise this with the senior midwives.
I agree a doula would be useful if this is an option for you.
I'm not sure a rape alarm would be a good option, if you are on a labour ward it may distress everyone else and newborn babies. There is an alarm in all the rooms and by the beds if you feel uncomfortable you can use that and you should have your birth partner as well to help make sure your wishes are met.