MID-CYCLE BLEEDING PERIOD 2 DAYS LATE HPT TEST RESULTS NEG

I AM 43, RECENTLY RE-MARRIED A MOTHER OF 3 CHILDREN, AGES 22, 18 & 8 MY HUSBAND IS 45 YEARS OLD.
FOR THE 1ST TIME IN MY LIFE I EXPERIENCED A MID-CYCLE PERIOD, I THINK...
I HAVE A 28 DAY, PERIOD LASTING BETWEEN 3 TO 4 DAYS.
I AM A HEALTHY/ACTIVE WOMAN
THE 1ST DAY OF MY LAST PERIOD WAS MARCH 10TH..MY HUSBAND AND I HAD UNPROTECTED SEX 2 DAYS AFTER MY PERIOD. EXACTLY 12 DAYS LATER COUNTING FROM THE 10TH, I BEGAN TO EXPERIENCE CRAMPING AND LATER BLEEDING, WASN'T HEAVY BUT MID TO LIGHT BLEEDING FOR 3 DAYS FINALLY ENDING WITH SPOTTING. JUST LIKE MY PERIOD.
SINCE THEN I'VE BEGAN TO NOTICE THAT MY ABODEMEN IS SWELLING, VOMITING, LIGHT HEADED, HEAD ACHES, BUMPS FORMING AROUND MY NIPPLES, FEELING AS IF MY PERIOD IS COMING ON AGAIN HOWEVER IT ACTLLY ISN'T DUE ON UNTIL NEAR OR ABOUT APRIL 7TH OR 8TH. IT IS APRIL 10TH STILL ON PERIOD, URINE TEST SHOW INVALID READING/NEG.
FOR A WHILE I BEGAN TO THINK IS THIS THE 1ST STAGE THE CHANGE OF LIFE...I AM UNCERTAIN.... I KNOW THIS MAY SOUND STRANGE BUT I ACTUALLY FEEL PREGRANT.