All the symptoms and 2 negative pregnancy test!

So im always on time every 28 days well im late iv been having mild cramping off and on for 4 days now that never happens! My boobs have been sore,stuffy head,headaches,back ache, mild dizziness! Plus cp is high,closed,and soft! Im honestly confused by the negative tests! I have had four children! But never had a neg test and all these symptoms its so weird! I used the 1$ test i looked them up they are 50 mlus I dont know if that makes a big difference in the fact I am 2 days late!