Rashi on Bereishit 49:3 tells us that Reuven was conceived with the first drop of semen that Yaakov emitted. How does this fit with the verses in Bereishit 29:25 to Bereishit 29:31, which seem to indicate that G-d only opened Leah's womb after she was the hated one, which was after Yaakov discovered that he had married Leah and had married Rochel?
וַיְהִ֣י בַבֹּ֔קֶר וְהִנֵּה־הִ֖וא לֵאָ֑ה וַיֹּ֣אמֶר אֶל־לָבָ֗ן מַה־זֹּאת֙ עָשִׂ֣יתָ לִּ֔י הֲלֹ֤א בְרָחֵל֨ עָבַ֣דְתִּי עִמָּ֔ךְ וְלָ֖מָּה רִמִּיתָֽנִי:
25 And it came to pass in the morning, and behold she was Leah! So he said to Laban, "What is this that you have done to me? Did I not work with you for Rachel? Why have you deceived me?"
כו וַיֹּ֣אמֶר לָבָ֔ן לֹא־יֵֽעָשֶׂ֥ה כֵ֖ן בִּמְקוֹמֵ֑נוּ לָתֵ֥ת הַצְּעִירָ֖ה לִפְנֵ֥י הַבְּכִירָֽה:
26 And Laban said, "It is not done so in our place to give the younger one before the firstborn.
כז מַלֵּ֖א שְׁבֻ֣עַ זֹ֑את וְנִתְּנָ֨ה לְךָ֜ גַּם־אֶת־זֹ֗את בַּֽעֲבֹדָה֙ אֲשֶׁ֣ר תַּֽעֲבֹ֣ד עִמָּדִ֔י ע֖וֹד שֶֽׁבַע־שָׁנִ֥ים אֲחֵרֽוֹת:
27 Complete the [wedding] week of this one, and we will give you this one too, for the work that you will render me for another seven years."
כח וַיַּ֤עַשׂ יַֽעֲקֹב֙ כֵּ֔ן וַיְמַלֵּ֖א שְׁבֻ֣עַ זֹ֑את וַיִּתֶּן־ל֛וֹ אֶת־רָחֵ֥ל בִּתּ֖וֹ ל֥וֹ לְאִשָּֽׁה:
28 And Jacob did so, and he completed the week of this one, and he gave his daughter Rachel to him as a wife.
כט וַיִּתֵּ֤ן לָבָן֙ לְרָחֵ֣ל בִּתּ֔וֹ אֶת־בִּלְהָ֖ה שִׁפְחָת֑וֹ לָ֖הּ לְשִׁפְחָֽה:
29 And Laban gave his daughter Rachel his maidservant Bilhah, for a maidservant.
ל וַיָּבֹא֙ גַּ֣ם אֶל־רָחֵ֔ל וַיֶּֽאֱהַ֥ב גַּם־אֶת־רָחֵ֖ל מִלֵּאָ֑ה וַיַּֽעֲבֹ֣ד עִמּ֔וֹ ע֖וֹד שֶֽׁבַע־שָׁנִ֥ים אֲחֵרֽוֹת:
30 And he came also to Rachel, and he also loved Rachel more than Leah; and he worked with him yet another seven years.
לא וַיַּ֤רְא יְהֹוָה֙ כִּֽי־שְׂנוּאָ֣ה לֵאָ֔ה וַיִּפְתַּ֖ח אֶת־רַחְמָ֑הּ וְרָחֵ֖ל עֲקָרָֽה:
31 And the Lord saw that Leah was hated, so He opened her womb; but Rachel was barren.