Why does the Torah insert the word "Gam" (the second time)?
Rashbam: By inverting the words "va'Ye'ehav" and "Gam," in which case the Torah is telling us that not only was Yaakov intimate with Rachel too, but that he also loved her more than Leah. 3
Tosfos ha'Shalem (1, citing R. Efrayim): A double inclusion excludes. He did not love Leah at all; she was Senu'ah.
Tosfos ha'Shalem (4): It teaches that he loved also Rachel's Shifchah [after he married her] more than Leah. 4
Ohr ha'Chayim: He was more regular with Rachel; his bed was fixed in her tent. And even though frequency usually decreases love - "Pen Yisba'acha u'Sne'echa" (Mishlei 25:17) - he also loved her more. 5
See Sanhedrin 22b.
Because of her good deeds (Seforno). The Seforno does not however, learn this from the word "Gam," but from the fact that the Torah sees fit to mention that Yaakov loved Rachel more than Leah.
See also Ohr ha'Chayim.
Why does the Torah insert the words, "Od Sheva Shanim Acheros"?
Rashi: To teach us that, in spite of what Lavan had done to him, he worked with the same integrity throughout the second set of seven years as he did throughout the first. 1
Tosfos ha'Shalem (10, citing R. Efrayim): They were unlike the first seven years, which were like a few days. These seven years, each day he longed for them to end. 2
What does it mean that he loved "Gam Es Rachel mi'Leah"?
Ohr ha'Chayim: He loved Rachel more than he loved Leah.
Malbim: He loved her more due to his hatred for Leah; a matter is recognized [more] amidst its opposite.
Ha'amek Davar: Initially, Leah did not feel that he does not love her; some men are not so close to their wives. After Yaakov married Rachel, and was very close to her, Leah realized that Yaakov does not love her so much, but did not yet feel hated. Only Hashem saw that she was hated (29:31).