Most likely the insomnia will worsen if you go to the 20mg dose. What I would recommend is giving the 10mg dose more time. Everybody's adjustment time for medications varies; some people adjust immediately, some within a few days, and some within a few weeks. You could try some OTC benadryl for sleep in the mean time (50-100mg). It would be a good idea to try to contact your psychiatrist to let him know what's going on. If the insomnia goes away after more time on the 10mg dose, then you will adjust more easily to the 20mg dose. I hope this helps. Good luck & take care.
The best would be if you could get specific advice from your own doctor. If you are unable to contact him/her until your next appointment, benadryl should be ok to try on a temporary basis until that appointment. There should not be any interactions with benadryl and your current medications. Another option would be to temporarily increase the dose of ambien, but I would NOT do that unless your own doctor was okay with it.