Sex position help!!

Ok so here's the deal I'm 5'5 and around 135 to 140 lbs and my boyfriend is 6'3 and about 250 to 300 lbs!! He's a big guy!! Any ways he is super sweet and I just love him so much! But because he's such a big guy I feel like we are already in a bit of a rut with sex positions, so does anyone have any tips for being smaller than your partner?? Thanks for any help!!