I don't want to get married in case I lose everything in the event of divorce, is this a normal outlook?

Background first as it's somewhat relevant to my mindset. My girlfriend (33) and I (28) have been together for 4 years. We met working at a pub, both on minimum wage, and have been very happy and have had 2 kids of our own in addition to another of hers from a previous relationship. Before her and the family, I was very frugal and "saved" around 75% of my take home pay however it usually went in some new gadget or tech that I wanted (including a few bitcoin that have since been lost) and didn't worry about it.
Over the 4 years I've gone through 5 job changes in IT and am now earning £35k annually which will increase next month after I start receiving on-call payments and overtime. She is still in the same job, currently furloghed, and has gradually received less of the benefits she was receiving before we were together so now receives around £100 a week.
After 9 months and finding out we were having out first daughter, I decided to buckle down financially and started matched betting with the view to buying a house for our new family. I made £16k over 18 months from that and eventually bought a 3 bedroom house for the 5 of us. I pay all of the bills and nursery costs and my girlfriend contributes to the shopping and retains what little she has for herself, which I don't mind.
Now we've both been talking about marriage and we would both love it but I'm hesitant because the relationship is very one-sided financially and in the event of a divorce, I would more than likely lose my house and 1/3-1/2 of my pay each month which isn't something I can bear the thought of being as frugal as I am. I know it will all be my contribution to the upbringing of my children but it just doesn't sit right with me. Are there other people that haven't gotten married for this reason?