Birthing a Ritual
I'm sorry to hear you're having a tough time, but the fact that you are able to take a step back to realize that you need to shift your mindset is already a huge accomplishment. Sometimes just knowing that you need a shift is enough to open your frame of reference to make more substantive change possible. Regardless, in a few short weeks, there'll be a new baby who will for sure cause a ridiculous amount of changes, no matter what else happens between now and then.
A little background for readers who may not be familiar, along with my usual caveat that I'm not a religious authority: A mikvah is a body of water, like a river, which is then used for a ritual purpose, or a kind of deep bathtub that has some "living waters" flowing into it. Mikvah can refer to the water itself or to the ritual whereby women immerse themselves once a month after their periods end and before they resume relations with their husbands or, as you experienced, before weddings and at other times of transition, including before childbirth. Men also sometimes immerse for various reasons, and more and more, especially in liberal circles, mikvah is being used for a variety of non-traditional but nonetheless very moving rituals.
The idea of mikvah is a really powerful one. It's very inspiring to me that in the middle of a hard situation, you're turning to Jewish ritual as a possible source of comfort. Since you are already familiar with Mayyim Hayyim, I highly recommend going to their website  and browsing their resources. They already have a ritual for the ninth month of pregnancy, so you could easily request a copy and see if it resonates with you.
Ritual Well  is a fantastic local resource run through the Reconstructionist Rabbinical College, and many thanks to Roni Handler, editor of that site, for her guidance that helped with this post. This blog post  from Ritual Well, written by Rabbi Danielle Stillman, has a lovely description of a variety of pre-birthing rituals. The site also has a whole pregnancy section , with pieces ranging from blessings for the mother-to-be  to an alternative baby showe r.
We are also very fortunate that in Philadelphia, there is a liberal mikvah available for a variety of uses. I definitely encourage you to check out and hopefully even visit the Mikveh at Temple Beth Hillel-Beth El  in Wynnewood. Lori Cooper, the director, offered some insights over email, saying that it's traditional to use the mikvah in a woman's ninth month of pregnancy "to pray for an easy delivery and healthy baby." Cooper said she has specific readings from a few different sources that she gives to pregnant women to read before immersing.
"I also make it a practice to sing, if desired, songs of hope, joy and comfort," she said.
Unrelated to your situation but perhaps relevant to others, Cooper noted that "there is a notion that the mikvah is a vehicle for acknowledging and transmitting blessings. Therefore, at our mikvah, a woman who is trying to conceive would be encouraged to use the mikvah."
Babies spend their time in the womb immersed in water (OK, technically it's amniotic fluid). The children of Israel walked through the Red Sea to become free people on the other side. Mikvah is the ritual that reunites a couple after a time of separation. As I said in my first post ever when explaining the name for this blog, "Legend has it that the biblical Miriam was followed around in the desert by a bottomless well, and she provided the Israelites with water throughout their wanderings." Water is, you know, essential, elemental, transformative. So perhaps you're on the right track in seeking out a mikvah.
Handler says the purpose of any ritual "is to encourage us to pause and notice how we have arrived in a particular moment, offer gratitude and to set intentions for the journey ahead."
I hope you are able to create an experience for yourself that does just what you need it to do.
Be well, and b'sha'ah tova,