Question: Do I need to count the omer? If so, should my husband wait to count the omer until he’s home so that he can count with me?
Answer: While Rambam (Temidin Umusafin 7:22) and the Sefer Hachinuch (306) hold that the mitzva to count the omer nowadays is mideoraisa, most poskim (Tosafos, Menachos 66a; Rosh, Pesachim 10:40; Ran, end of Pesachim) hold that it is derabanan. The Ran explains that the Torah obligation is dependent on the korban haomer. Nowadays, we continue counting in commemoration of the mikdash.
There is another machlokes as to whether women are obligated at all. Ramban (Kiddushin 34a) holds that women are obligated while Rambam (Temidin Umusafin 7:24; Sefer Hamitzvot 161) and the Magen Avraham (OC 489:1) hold that as it is a time-bound mitzva, women are exempt.
The Mishna Berura (489:3) quotes the Shulchan Shlomo (489:3) who writes that as women will probably forget to count one night they shouldn’t count with a beracha at all. Nonetheless, the Aruch Hashulchan (OC 489:4) and R’ Ephraim Greenblatt (Rivevos Ephraim 1:327; 6:257:23) write that women do keep this mitzva nowadays and should count with a beracha; especially as people set alarms nowadays to remind themselves of such things, women should do so, too.
The Shulchan Aruch (OC 489:1) writes that one should start counting the omer immediately after Maariv on the 2nd night of Pesach. While some count after the Seder for Kabbalistic reasons (Yesod Veshoresh Ha’avoda 8), R’ Yaakov Emden (She’elas Yaavetz 2:83) wrote very strongly against this practice, writing that it is best to count straight after maariv as one shouldn’t eat before one has counted (Rema 489:4). Additionally, it is better to count the omer together with a minyan. The Piskei Teshuvos (489:1) writes that most poskim (including the Aruch Hashulchan OC 489:11) agree that one should count before the Seder.
The Mishna Berura (Biur Halacha 489:1) writes that the reason why we daven maariv before counting the omer is because people used to daven maariv before nacht when it was too early to count. R’ Moshe Feinstein (Igros Moshe OC 4:99 in a letter to R’ Ephraim Greenblatt) challenges this and says the reason is because we follow the rule that tadir ve’sheino tadir, tadir kodam, the mitzva that we do most often takes precedence. Nonetheless, as it is better to count the omer together with a minyan, we do so on motzaei Shabbos before we go home to make havdala.
R’ Ephraim Greenblatt (Rivevos Ephraim 6:257) writes similarly that while one should daven maariv first, if one walks into shul while they are counting the omer, one should count with them.In conclusion, your husband should ideally count in shul after maariv. He should remind you to count, or you may want to set yourself a reminder.