Worried and would like some friendly advice?

Georgie • 18, happily engaged and pregnant with baby number 1! 😍
Hey, so since August last year I've been pretty ill (having multiple surgeries, being on multiple different antibiotics) and so as you can imagine, pretty run down. 
Me and my partner have been trying for a baby for coming up to a year now and sadly no luck, but the past 3 periods I've missed and I've taken pregnancy tests and they're all negative, but I get this cramping (exactly like my period cramps) only on the left hand side of my lower abdomen... Any help would be appareciated? X