Help...

I'm 23 weeks pregnant , is it normal for me to always feel agitated & exhausted like ive walked in the dessert for days?? I can't stand up for long periods of times nor walk too much because I start feeling shortness of breath , my heart starts pounding and I get very light headed , I also can't stand the heat I need to have cold air blowing in my face all day everyday or either I feel like I can't breath and its scary idk if its normal 😞 anybody know ??