Should I just do it and try for another baby???

Okay so I’m 31, soon to be 32. We don’t have the space and there are a bunch of other obstacles, and I also have 18 month old twins, and an autistic teenager. This may be my last chance to conceive, and have my last baby. My period is about to start and my fertile window should be the first week of December, so the baby if conceived would be a Christmas miracle! If we try, we decided to leave it up to date and just try diligently for only 2-4 months, and if it happens it was meant to and if it doesn’t it wasn’t. I’ll never be able to afford fertility treatment at a later date when my fertility is all but gone. This really is my last chance. What do you think? And I had vaginal delivery with my first, but a pushed c section with my twins. What do you think my chances of a VBAC are? Also, what’s the best way to check CM? Can I use a q-tip? Thank you and Good bless all!