I know this may sound a tad harsh but it really isn't intended that way and i'm not sure how else to word it :?
But basically your situation isn't going to go away.
So the sooner you action rather than stress over the sooner you can relax knowing you are sorted.
Right now your mom is in a very difficult place, she is keeping something from her partner.
Your parents love you, they may be misguided in how they express that sometimes but then parenting doesn't come with a handbook unfortunately.
The sooner you get this pregnancy out in the open the sooner everyone can relax, and at 17 weeks if you don't tell him soon - you'll be having some explaining to do when the bump shows itself.
Tell them you wnt to get a job but that to get a job you need to be able to secure transport to and from.
I notice you are in the uk - motorway services are always hiring people and they provide transport.
Also see if there isn't a milward-brown near you - they usually run a mini bus too and the work is dead easy for good pay and they know that people are usually going to be with them short term anyway, although someone did go from nothing to associate director in 6 years, so there is opportunity to develop.
Here ya go email them a cv
hr [at] uk [dot] millwardbrown [dot] com
it's just market research
or look around/ask around/yellow pages to see if there are any other market research places in your local area many of them provide mini bus transport.