Oh I just typed a long post but lost it 
I have a question but I know this is a contentions issue so I want to preface by saying I am not anti trans and absolutely agree that trans people should be protected. I admit a little ignorance, so please accept my apologies if I offend. I am also just starting to learn about this so am getting my head around cis, trans, trans + etc, so please forgive me if I get something wrong - please be assured I mean no offence and feel free to correct me. When I say male/female/etc I just mean in layman's terms.
I get that a trans woman is a woman - I agree with that. I also understand that as soon as someone identifies as a particular gender, that's that, they are protected against discrimination for being trans. They don't have to have seen a counsellor, have a doctor confirm it, get a certificate... again there is nothing that makes me vehemently opposed to this, I think it is the right thing.
I understand that a trans woman can use, for example, women's changing rooms and toilets, and I think thisnis the right thing - I have no problem with a trans woman being in the same toilets as me or whatever. I don't feel comfortable in communal changing rooms with anyone, trans or not, as I am sheepish, but if I have an issue I move myself, I don't expect anyone else to move because I feel uncomfortable. Toilets, I don't really mind as the cubicle is lockable and most of the time people keep themselves to themselves.
I know someone (friend of a friend so i don't know full details, but i have met them so it's not urban legend) who was born male and brought up as a boy using boy's toilets etc; as a teen they decided that they identified as female, started treatment and counselling etc, and started using women's facilities. Then in their late 20s they changed back, and started identifying as a man again, using men's toilets etc. I don't have an issue with what they did at any point.
However, my confusion comes when there is a potential abuse of this or a conflict of rights.
Say I had an ex partner who was harrassing me, but in a very subtle way that I couldn't prove or make a complaint about. Say we worked in the same place, he could claim to have decided to identify as a woman, even if it were a blatant lie, and follow me into the toilets because he knows that very act is intimidating me, there is nothing anyone could do to challenge him? If a trans argument is "what's your problem with a trans person with a penis using the facilities designed for people with a vagina?" then surely the counter argument is what's their problem with sharing with other people with a penis? I know some places now have accessible toilets for trans people to use if they so wish, but I don't think i believe they should be obliged to (much like, say, a breastfeeding room - it's there if you want it and feel more comfortable there, but you have a right to do it elsewhere). If anyone can choose, in theory, to identify with a particular gender as they please, what is the point I having gendered facilities at all? I actually don't think that's a terrible solution...
Another thing I struggle with is as someone who has been sexually assaulted several times, always by a man - I was sexually assaulted asa child and find certain situations triggering, though with careful counselling I do not generally fear people with penises. However, what about things like rape crisis? If a person who identified as a woman applied for a job as a rape crisis advsior they could not legally be turned down for having or once having a penis, right? I would feel extremely uncomfortable if I had just been raped and then had to have rape crisis advice with someone who possibly has the potential to attack me in the same way. Or i would feel extremely uncomfortable to have an intimate medical or forensic examination performed by someone who in their own head identifies as a woman, but as far as I am concerned is someone with a penis - it would make an already distressing situation worse. So if a person has a very very genuine reason for not wanting to take the risk, they can't have tgat allowance because of the trans person's rights? Nb I don't mean if someone just doesn't like the idea of transsexualism - I'd see that as the same as refusing to deal with someone of a certain race or whatever.
What about the potential abuse, again by men? What if an abusive man claimed to identify as a woman, they need to provide no proof of this, what if they got a job in a refuge to prey on very vulnerable women?
There are very good reasons for certain parts of life being men/women only (again I mean lay men's terms) - are the trans rights the ones which take priority?
Sorry this is very garbled, I hope this makes sense!