I'm 12 weeks pregnant and Claritin (loratadine) is not touching me. History of premature membrane rupture at 27 weeks, what allergy meds can I take?

Several options. For pregnant patients with allergic rhinitis there are several options that start with the most benign to those that are cat b in pregnancy ( which means as best as we can tell the med is safe). Nasal saline then otc Nasalcrom and then nasal steroids ( only those that are cat b in pregnancy).
Ask. Always best to ask, but usually Benadryl (diphenhydramine) is allowed by OB doctors. There are also prescription nasal sprays that are available.