Worried about always being off work with pregnancy complications

Hi everyone,
Sorry in advance for really long post. 
I'm a little (well, a lot) worried
I'm a psychiatric nurse and I work 13.5 hours shifts and rarely have time for a break. 
I work  on a unit with violent and aggressive patients ( I was hit in the stomach 4.5 weeks preg). 
Risk assessment done but I'm still around patients and not a great deal has changed. Work have not offered me an alternative for being on the ward despite being aware of the risks. 
I'm currently on disciplinary for attendance, prior to pregnancy and I've been told my attendance needs to dramatically improve. I often feel like work don't take me seriously and just think I'm overdramatic and I'm frequently reminded by them that "pregnancy isn't an illness". 
 I'm currently 11 weeks 5 days. Around 5,5 I had a bleed and was off work for 2.5 weeks. After only 2 weeks being back I had a very heavy bleed at 10 weeks, following tests I was told I had probably lost the baby and needed to go back in for ultrasound to make sure my uterus had expelled everything. 
However, during my scan, my little dancing jelly bean was doing lovely whirls and twirls in uterus and had very healthy/strong heartbeat. I was told I had a viable pregnancy and miscarriage risk was 1%. But, they gave me a sick note for 4 weeks on the basis of having heavy bleed. But as I am already on disciplinary for attendance I rushed to get back to work. I had the rest of the week off work and went back today. (3 weeks early). 
4 hours into my shift I had another bleed and came home early, now off sick again. Bleeding stopped and no clots. Still have some abdominal pain. Have scan on Friday and just trying to rest. 
Every time I go into work I seem to have another bleed, like I'm pushing myself too hard, maybe. Plus the stress and anxiety of the potential for violence can't be helping me or baby.
Anyway, I'm getting really worried about time off work and potentially being disciplined further. I know pregnancy related illness should not count but the company I work for tend to have their own rules. When I'm at work I'm at risk of being attacked by patients and I constantly experience high levels of stress and pressure. I just feel like I'm not being taken seriously and I worry so much. Work told me any more time off and I'll need to start maternity leave but I was sure that it couldn't start until 29 weeks. I've chosen to go at 32 weeks and using annual leave for 3 weeks before that. 
Has anybody else been in this position before or can anybody offer any reassurance? 
Thank you in advance xx