WATCH: Nathan Griffith Slams Jenelle Evans' Sex Life, Weight Gain, & Accuses Her Of Drug Use!

The sit down with Jenelle Evans and her ex Nathan Griffith didn't end pretty!

In a sneak peek clip for the Teen Mom 2 reunion special, Nathan and Jenelle discuss their custody issues over their one son, Kaiser.

"I even have a text message that says, 'hey if I give you pictures, it still won't be good enough, so how about I meet up with David Eason and buy the stuff in front of you,'" Nathan says. "He has no highchair, he has no sippy-cups, he doesn't have food for him, he doesn't have anything," Jenelle fires back.

After Jenelle laughs at Nathan for not having a license, he reveals the reason why he is fighting for full custody. "My son is in an unstable environment with two drug addicts, where you see weed in the background smoking constantly, now you have these mysterious illnesses, you're not capable of taking care of him, you are totally unstable." However, Jenelle slams him and says, "Just like how your lawyer wrote on the complaint that my sex is painful, what does that have to do with Kaiser, please tell me."

Nathan suggests that she shouldn't discuss her "sex life on on national television" before she fires back, "I'm sorry it bothers you that I talk about my sex life, sorry I'm not with you anymore."

Nathan fires back, "I don't want you to be with me anymore, I mean how much pounds are you going to gain? Like 30 or 40 pounds?"

Watch the clip above to see the tense conversation between Jenelle and Nathan! The Teen Mom 2 reunion special airs Monday at 9pm ET on MTV!