Limited symptoms

My first pregnancy was horrible. I had severe morning sickness the whole pregnancy until I gave birth. My second pregnancy I didn't have any morning sickness and it ended in a missed miscarriage. My third pregnancy ended ad a chemical. I'm now on my fourth pregnancy and I don't have severe morning sickness. The only symptoms I have are lower back ache, bloat, nausea that comes in waves sometimes severe sometimes not, headaches, and food cravings/aversions. Does this mean something is wrong? I can't shake the feeling that this is a bad sign. Anyone have any input?