well there is such a thing as false pregnancy where your mind is tricked into believing you are when you're really not. in extreme cases you might even get a baby bump. this has also been seen in other species like cats, mice and pigs.
a pregnancy spell can increase your chances, not 'say these words and poof you're with child' like i said, it's usually 'take these herbs, say this chant and have sex within the hour' or whatever. male fertility is also a factor, so most fertility spells i see usually asks as a step the man takes part as well. [i have seen some specific to woman like the moon water charging, but that one i'm skeptical about it's potency since moon water = pregnancy?] still, the safest bet is to get your tubes untied and try then. best of luck to you.