Having sex in the missionary position is the only way to get pregnant
Sex can be fun even if you are trying to conceive. If there is penetration (the deeper, the better) and as long as your partner ejaculates in you, the position you have sex in does not matter. Remember to have some fun and try out new positions!
If you do require additional lubrication, it would be good to ensure that the brand is safe for couples trying to conceive. There are even brands of lubricant that are specially formulated for couples trying for a baby.